How-to: Get Better MPG out of your Rover or MG!

chrisoverson · Mar 21, 2012

How to get Better MPG out of your Rover or MG

Hi all. As we get lots of posts on the forum asking about fuel economy and people who think they should have better MPG than they currently do, I thought I'd post up a guide on a few things I've picked up.

Now this is written with my knowledge of the K-Series in mind, but the driving tips and some of the mechanical ones will apply to any car, diesel or petrol.

I've been very enthusiastic about saving fuel, and as many people might know I'm working on a live MPG display addon for all K-Series cars and eventually others. This has helped me to realise how the fuel delivery works and better optimise my fuel economy.

For those of you in europe or other countries, MPG is the standard for guaging fuel effeciency in the UK. One UK gallon = 4.54609 litres.

This will be split into three sections:

Mechanical Checks, Mods and Engine Maintainance
Driving Techniques
Fuel economy Myths

This is all going on my own experience and knowledge, and I'm sure there will be a few mistakes or additions to be made, but I hope that this guide will help you. I hope an admin will find this worthy of a sticky

Official Rover MPG figures from Owners Handbook

Here is a good place to start; how do you know how well you are doing if you're not sure what your car should get from new!

Here are the figures for the 200 series:

URBAN:
R211 8v is 33.8mpg urban
R214 8v is 30.4mpg urban
R214 16v is 28.6mpg urban
R216 16v is 28.2mpg urban
R218 16v is 28.3mpg urban
R220SD is 36.3mpg urban
R220SDi is 37.0mpg urban

EXTRA URBAN:
R211 8v is 49.2mpg extra urban
R214 8v is 52.8mpg extra urban
R214 16v is 52.0mpg extra urban
R216 16v is 50.5mpg extra urban
R218 16v is 48.4mpg extra urban
R220SD is 62.6mpg extra urban
R220SDi is 63.0mpg extra urban

Figures for the ZR / 25 (thanks to roverlike)

URBAN:

1.1 is 32.0 mpg urban
1.4 is 31.1 mpg urban
1.6 manual is 30.6 mpg urban
1.6 auto is 26.2 mpg urban
1.8 manual is 28.5 mpg urban
1.8 auto is 24.7 mpg urban
1.8 - 160 is 27.1 mpg urban
2.0 diesel is 39.2 mpg urban

EXTRA URBAN:

1.1 is 51.3 mpg extra urban
1.4 is 51.1 mpg extra urban
1.6 manual is 50.6 mpg extra urban
1.6 auto is 50.9 mpg extra urban
1.8 manual is 49.4 mpg extra urban
1.8 auto is 45.0 mpg extra urban
1.8 - 160 is 48.7 mpg extra urban
2.0 diesel is 68.3 mpg extra urban

Figures for 45/MG ZS (thanks to JoeyTaffy93)

URBAN:

1.4 is 30.4 mpg urban
1.6 is 29.4 mpg urban
1.8 manual is 29.2 mpg urban
1.8 automatic is 23.8 mpg urban
2.0 is 20.3 mpg urban
2.5 is 20.0 mpg urban
2.0 diesel is 38.7 mpg urban

EXTRA URBAN:

1.4 is 49.4 mpg extra urban
1.6 is 48.7 mpg extra urban
1.8 manual is 48.3 mpg extra urban
1.8 automatic is 43.2 mpg extra urban
2.0 is 42.2 mpg extra urban
2.5 is 41.4 mpg extra urban
2.0 diesel is 66.4 mpg extra urban

Figures for Rover 75 (again thanks to JoeyTaffy73 )

URBAN:

1.8 manual is 26.1 mpg urban
1.8 automatic is 20.1 mpg urban
1.8 turbo manual is 25.0 mpg urban
1.8 turbo automatic is 22.1 mpg urban
2.0 manual is 20.9 mpg urban
2.0 automatic is 17.6 mpg urban
2.5 manual is 20.2 mpg urban
2.5 automatic is 16.8 mpg urban
4.6 automatic is 15.4 mpg urban
2.0 manual diesel is 36.9 mpg urban
2.0 automatic diesel is 28.3 mpg urban

EXTRA URBAN:

1.8 manual is 46.5 mpg extra urban
1.8 automatic is 36.3 mpg extra urban
1.8 turbo manual is 46.3 mpg extra urban
1.8 turbo automatic is 42.8 mpg extra urban
2.0 manual is 40.3 mpg extra urban
2.0 automatic is 34.1 mpg extra urban
2.5 manual is 39.4 mpg extra urban
2.5 automatic is 32.8 mpg extra urban
4.6 automatic is 26.9 mpg extra urban
2.0 manual diesel is 63.1 mpg extra urban
2.0 automatic diesel is 54.7 mpg extra urban

You may well notice the 25/ZR figures are slightly better than the earlier 200s. This will mainly be down to the newer engine management

If your car is getting significantly lower than these values and you drive efficiently then chances are something needs fixing or cleaning! Bare in mind these are the official figures for when the car was brand new out of the factory, with zero wear, zero carbon deposits and so on. Generally it seems people assume cars get a lot worse over time with regard to power and efficiency, but I wouldn't say that they do very much as long as they're looked after and driven responsibly

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1. Mechanical Checks, Mods and Engine Maintainance

To get the best miles per gallon out of your car you must be sure it is mechanically sound.

Anything that restricts the flow of fuel, air, or exhaust gasses will prevent your engine from running at its optimum efficiency.

Important engine checks are:

Check your air filter regularly, replace if dirty and remove any debris from the airbox. This is really the only filter you can inspect and replace without worry. Any restrictions here will stop the engine from breathing properly and hinder performance.

Replace your fuel filter yearly. Any restrictions to the fuel flow will force the engine to attempt to inject more fuel to compensate, resulting in poor performance and poor MPG.

Change your oil using the recommended grade (most engines use 10w40) within the standard limits. Some people recommend once a year, or every 6,000-10,000 miles. When the oil is dirty and full of tiny particles, it is no longer able to lubricate your engine as well as it once did. The internal combustion engine is only around 33% efficient as it is due to friction, any increased friction caused by old oil or low oil (check level often) will cause lost power and fuel economy.

Always replace your oil filter at the same time as the oil. As pointed out by D.Ilbert there's no point pumping clean oil through a dirty filter, do both at the same time.

General modifications and their effect on MPG:

Any modification designed to increase engine performance, power or high end RPM will almost certainly require extra fuel to get it. If you modify your engine, whether through induction, exhaust, cams or remaps if you want extra power, you will normally have to burn extra fuel to get it. The only real modifications other than a clean engine that will improve MPG are possibly remaps, and a clean flow of air.

K-Series engines do not really suffer with problems in air induction, so fancy induction kits and "ram" air systems may look fancy, may cost a lot and may sound lovely, but will do precious little to improve your fuel economy. The tried and tested setup recommended by most here is the standard airbox, using a K&N panel filter.

The great Cone Filter argument

It has often been said that adding an open cone filter will hinder performance and MPG. This is not strictly true. A cone filter sucks in air from the engine bay rather than from the front of the car, which means the air entering the engine will be warmer than it would be directly from the outside.

This means it is not as dense, and the ECU works by determining the amount of oxygen entering the engine and enters a proportional amount of fuel in order to maintain the ideal fuel to air ratio. Because less fuel and less air enter the engine, there will be less power. However, because there is less oxygen entering the engine, the ECU has to inject less fuel to maintain the ratio, therefore there is actually a slight increase to the MPG.

Also, if you are worried about performance you're hardly likely to be revving the nuts off your car in 1st gear around town. Performance counts when you're going fast, and once that happens there should be sufficient fresh cold air entering the engine bay through the grille to provide plenty of oxygen for the engine to breathe.

The other benefit of a cone air filter or hot air intake system is it's effect on pumping losses (see below).

Exhaust modifications:

Exhaust modifications are a commonly discussed subject on the forum, particularly "decatting" and it's advantages and disadvantages. To put it simply backpressure is never, ever a good thing. You want a clean flow of exhaust gasses and no pressure put back on the engine. However you do need DELTA pressure.

Delta pressure is caused by cleanly flowing exhaust gasses making their way out of the pipe. In a perfect system, the pipe should be just big enough to not cause a restriction, but no bigger. Exhaust comes out in pulses, and as one pulse zooms down the pipe, if the pipe is tight enough it leaves a vacuum behind it, which sucks along the next pulse of exhaust gas.

The best way to explain this is like syphoning water from a fish tank. You suck on one end, creating a vacuum, then quickly stick the tube down in a bucket. The water comes pouring out of the end due to your vacuum, and then that water creates a vacuum in the pipe behind it sucking along the next lot and so on giving you a continuous flow of water.

The exhaust system works in the exact same way. If the pipe is too small, there is a restriction, if too large, then the vacuum effect (delta pressure) doesn't happen, and the engine has to actually pump the gas out using the exhaust stoke of the piston, which wastes power. It has been proven time and time again that decatting a K-Series might sound nice, but will decrease usable power and fuel efficiency, and this is why. It upsets the Delta pressure!

If you really do want to modify your exhaust, speak to a proper professional about getting the right size to suit your engine and your mods. On a turbo car the setup is slightly different as the whole idea is to get the gasses through the turbine right by the engine as fast as possible, so bigger exhausts are used.

Another factor is tyre size. The more rubber in contact with the road, the more grip. Great for zooming round corners, bad for efficiency. The more friction your tyres get on the road surface the harder it is for the engine to turn the wheels. This is why keeping your tyres at the right pressure is vital (discussed further down).

Pumping Losses - The key to creating efficiency

There is an additional benefit to fitting a cone filter or hot air feed if you are interested in MPG. When you are pushing very lightly on the throttle, the engine is sucking in the least amount of air, and therefore the least amount of fuel is being injected. This is great, however believe it or not this puts the greatest amount of strain on the piston's inlet stroke.

As most of you will know our engines function on the basic four stroke principle:

1) Piston goes down, sucking in fresh air, along with fuel in a petrol (inlet stroke)
2) Piston goes up, compressing the contents of the cylinder (compression stroke)
3) Spark plug ignites, or diesel is injected and autoignites, driving piston downward (power stoke)
4) Piston goes back up again to push exhaust gasses out.

This cycle can be seen here: http://auto.howstuffworks.com/engine1.htm

Now from this it is obvious that the piston moves four times but only generates power on one stroke. This is why an engine is so inefficient
at converting fuel energy to motion, but its the best we've had for a long
time. Anything that adds load onto those piston movements will take away
power generated in the power stroke.

When the piston goes downward on the inlet stroke it sucks in air from outside. If it has to suck this air through a very small opening like a nearly closed throttle body then it has to suck harder, creating a higher vacuum. It is like trying to suck through a pinched drinking straw. This makes it harder for the piston to go down on the inlet stroke, slowing the engine down and sapping precious power.

When you use hot air instead, you have to open the throttle a tiny bit further to get the same amount of oxygen through, which means less restriction on the system and allows the piston to go down more easily.

This is one reason why diesels are so efficient; their throttle is always wide open (they have no throttle plate) and they simply inject fuel as required. A turbo is also efficient here because it creates a positive pressure in the inlet manifold pushing air into the engine rather than it having to suck - even at 0psi it is still eliminating the manifold vacuum!

The perfect air intake system for efficiency would allow the engine to draw in hot air when accelerating or at higher throttle openings, but during idling and very low throttle opening conditions allow cooler air in. This is because whilst hot air contains less oxygen due to its low density it is also more viscous, and more difficult to fit through the smaller opening. If you check my Super Efficient 1.8 Thread I will be attempting to install a system in my car that draws red hot air from above the exhaust manifold, and cold air from the front of the car, then controls the flow of each to regulate intake air temperature. The advance of this system would be that if you just wanted to switch back to pure power (even if it only added 1bhp) then all you have to do is shut off the hot air feed electronically and away you go.

The exhaust system works in the same way. Any restrictions in the exhaust means the engine has to push harder on the exhaust stoke, sapping more power from the engine (see above).

Interestingly at low throttle openings while the inlet stroke puts load on the piston due to the increased vacuum, there is less pressure during the compression and exhaust strokes becuase there is less to compress, and less exhaust will be generated to push out. This is part of the reason why small engine loads are so much more efficient than high engine loads, all we need to do is balance it so all of the strokes suck the least amount of power from the engine allowing us to get the most output for the least input

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The main important factor with mods and MPG is this, you modded your car to be fast, therefore you will want to drive it fast. You don't mod your car to reach 60mph quicker or go 20mph faster so you can cruise along barely nudging the throttle. If your the kind of person who cares about performance chances are you will have a lead foot, and here is where you suffer your performance hit. 99% of the time you can't blame your engine, exhaust or induction kit, as often due to the lovely sound they make you will be slightly generous with the throttle just to hear them. This seems to be the case with most things such as cone filters, as I have one myself and it is very tempting to dip the throttle for a second or two to hear the K-Series Purr.

Other mechanical checks:

Any added form of friction will make your engine work harder to maintain speed. Therefore you must be aware of potential problems such as brakes seizing on, bearings going or similar issues. It is recommended that if you hear anything catching check it immediately, and periodically check your brakes after a drive to see if any of them are particularly hot, which would point to siezed calipers or warped discs.

All electronics will cause a performance and MPG loss as well. Anything that uses power when the engine is running puts a load onto the alternator, which will cause the engine to work harder to turn it. An interesting thing to note is that even if you use up power when the engine is off (playing your music etc.) which could drain the battery slightly, will force the engine to work harder as soon as it starts again, draining fuel. You may not notice the change as these engines are designed to compensate for extra alternator load by increasing RPM to match. You'll probably notice after having trouble starting your car in winter for example or when you have a flat battery that your engine will rev higher for a little while to recharge the battery again.

Using high wattage sound systems or bulbs etc. when not needed will therefore put an extra load on the engine and decrease MPG.

If your wheel alignment (tracking) is at all out then your MPG will suffer greatly too as it is having to drag extra rubber where it does not want to go, causing increased friction. It is a very good idea to have your tracking checked fairly regularly, at least once a year or if you have new tyres put on.

Tyre pressures - something you have no doubt heard time and time again. Put simply if your tyre pressure is low it means that your tyre will not bulge out in the middle as much, but more "flop". This means more rubber touching the road, meaning increased grip, but more power needed to keep the wheels moving. Therefore low tyre pressures will cause you to suffer. DO NOT overfill your tyres to increase MPG however. While it will almost certainly work, the difference will be minimal to your wallet, but could be deadly on the road. As above, higher pressure will mean reduced grip. Fill to the recommended amount and check weekly. It is important to keep both sides balanced as quite often one side will lose pressure faster than the other, due to loads or tyre wear and alloy wheel corrosion causing a bad seal.

2. Driving Techniques

You've probably been told dozens of times that fuel efficiency all comes down to how you drive. This is not strictly true but it certainly makes a huge difference.

Here are some driving tips I've adopted since owning my K-Series Rover. Most of these tips will apply to everyone in any car.

When coasting (rolling downhill with zero throttle), keep revs above 1600RPM (change down if you must) and do not put the clutch down, as the ECU in the K-Series will turn off the fuel injectors and let your engine run on the momentum alone when the RPM is above this point. Do not touch the throttle at all unless you have to, as the second you do fuel will be injected again.

Try to avoid stopping completely where possible when approaching junctions and roundabouts etc. You obviously have to slow right down at times, and sometimes it is unavoidable to stop, but even if the car is moving at just 3-5mph then it's a lot easier for the car to increase speed, as it is less work to accelerate than it is to start from stationary. This applies anywhere, including in traffic, giving yourself room will make a big difference; if you keep yourself moving even at a slow speed it means less work for the engine.

An extension to this is when moving up hills in traffic, do not allow the car to roll backwards before moving forwards, as the engine then has to reverse the direction of travel as well as moving you forwards. Use the brakes to hold yourself still before moving off to limit the load on the engine. Obviously the harder the engine has to work, the more fuel is injected and used.

Also when stopping at traffic lights, there is no point using fuel to drive right up to them and stop, so if you're coming up to a light (also applies to junctions) and you know you need to stop, take your foot off and coast there, the aim being to use zero fuel on your approach. It doesn't matter how slow you get there (within reason, if you're being followed for example) it won't hinder your progress as you would have to stop anyway when you get there. If you're lucky you can time it so the light changes to green before you stop, so you can carry on straight through, again saving precious fuel.

When sat with the engine running on idle you don't have to worry too much as I've discovered this uses a minimal amount of fuel. I recently estimated the cost to be around 3p per minute, or £1.50 per hour. There is a widespread theory that the car uses a lot of fuel to start up, and while this is true to an extent, in most cases if you are going to be idling for more than 10 seconds then you are better turning your engine off, as you burn more in 10 seconds than your car takes to start.

The very best ways to drive are to allow your car to use momentum to travel rather than fuel where possible, so if you have any downhills, use them to accelerate then use as little pedal as possible for as long as you can maintain speed afterwards. If possible keep your engine above the magic 1600RPM with your foot off the pedal for free travelling!

Don't ever accelerate faster than you need to if you know you have to slow down again soon after (e.g. gap in traffic etc) constant smooth driving is the key. Your car uses a miniscule amount of fuel to maintain a speed compared to what is uses in getting there, remember that.

Any exessive acceleration should be limited. E.g. coming onto a main road with little or no traffic behind you, there's no reason to test your car's 0-60 speed every time, just casually go along changing up as you accelerate to keep your RPM relatively low, using as light a foot as possible. The ECU injects fuel depending upon your throttle position, not your speed. The further down you push the pedal, the more fuel you use, simple as that. I understand this to be frustrating at times, but believe me the benefits are worth it, your car will last longer, you will have more money in your wallet, and the ride will feel so much smoother and more comfortable.

Try to enjoy it. I sometimes try to picture I'm a professional driver trying to make the drive as smooth and as comfortable as possible for my passenger. It works well, especially round town, even if it sounds a little odd

Another thing I've really noticed from my MPG monitor on my computer is that the ECU respons to absolutely TINY changes in throttle position. If you have your foot lightly touching the pedal giving it enough power to climb the hill or cruise along, if you put it down just a minute fraction more, even if the car doesn't noticably speed up the MPG instantly drops. Try to touch the pedal as lightly as possible while maintaining the speed you want.

As I've said above, the ECU injects fuel based on your throttle position. I've often found the best way to maintain maximum efficiency is to change gear or speed so that you have to touch the pedal as little as possible to maintain speed. Even if that means going 3mph under the speed limit it is well worth it in MPG rewards.

The key thing is to not only use as little fuel as possible, but get as much out of that fuel as you can. The gentle smooth driving means you are focused less on hammering your car, and makes you much more aware of the road around you allowing you to plan your driving better. This will make you safer, but also allow you to time gaps, lights and junctions better in order to reduce the amount of time you spend on the brakes. The brakes are the evil being where MPG is involved, as essentially every time you apply the brakes you are converting all that kinetic (moving) energy you have created with your precious fuel into useless heat, and degraded brake pads. Obviously you must use brakes, but by driving smoothly, coasting gently to a stop at lights and junctions, and watching ahead you can reduce the use of them considerably.

When travelling on motorways and you aren't desperate for time, you would be amazed how much difference travelling at 56-60mph rather than 70mph will make. It's annoying at first, but has a couple of massive advantages. The first is it's a much more efficient cruising speed for the vehicle, creating less drag and requiring less fuel. The second is that once you get used to it (which won't take very long at all) your urge to overtake anything doing less than the speed limit will be gone.

When you are on the motorway doing 70mph or slightly more if somebody in front of you does any less, then you instinctively put your foot down a little and pass them. Over a long journey you could easily do this 60 or 70 times without even realising it, but every time you did that extra fuel has been burned away. What I do is find somebody travelling at 60mph or so (and they're always there) and sit behind them at a safe distance for as long as you can, chances are they will stay at that speed. After a short while you get acustomed to it, and you'll find yourself much more relaxed and enjoying your drive more, having to concentrate less on multiple lanes and overtaking, speed cameras and police etc etc.

The reduced drag from having a vehicle in front of you will make a difference too, so where possible find yourself a van or a lorry. Do not sit too close behind for obvious reasons, make sure you can be seen.

Using those motorway driving techniques I managed to drive all the way from Devon to Dartford ( 4.5 hours roughly ) and I averaged 50mpg. This is out of a vehicle that shouldn't get more than 40mpg according to rover when new! My friend's 2007 ford focus can only just scrape 36mpg on the motorway, with the same engine size (1.8). So these cars can and will do it.

What's more I was so relaxed all the way there that I didn't even stop once, and wasn't even needing my standard car sweets to calm me down. 4.5 hours solid driving with one bottle of water and no more

(I should add I hate distance driving normally, before I adopted these techniques).

Drive this way and your car and your wallet will love you for it. Not only do you save fuel but your car will be under less strain, the brakes will be in better shape as they are used less, and the tyres, gearbox and other components will thank you too

.

I'd like to add at this point that I've had my car for 8 months now ( 1.8 litre Rover 200, no modifications other than alloy throttle body to prevent sticking ), and after adding up the miles I've done and all of my fuel receipts which I save as I put them through my business, I have calculated that I average 40-42mpg. This is 90% urban driving, and only about once or twice a year do I drive on the motorway, most of my driving is around my local town repairing computers, with lots of short trips. It is perfectly possible

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3. Myths

We have already covered the myth of fuel usage during engine start, if you are wondering about that one.

Here are a few of the ones I've explored:

Higher octane fuels, BP Ultimate fuels etc. These are all pretty much useless in our K-Series rovers. Any fuel that uses higher octanes are designed for cars that are either tuned to use it, or that have knock sensors to adjust the timing to suit the different fuel. You will not benefit by using these fuels, and as for the rest of the stuff they put in them you can get the same effect by keeping a clean fuel filter and whacking in a bottle of Wynns fuel system cleaner every couple of months (I personally recommend this).

Reddex. This seems to be the first thing to dump in your tank when performance/mpg is limited for many people. I would advise against it... many people have experienced no benefit, and sometimes even less performance following the use of Reddex. Whilst it does contain additives to clean your fuel system, standard petrol has enough of those in anyway these days.

Letting the tank get near empty. There's been little or no evidence that driving on low is harmful, as the fuel that goes in should be clean for one, secondly your fuel filter is there for a reason, and also your fuel pickup is in the bottom of the tank anyway.

Wierd fuel guage readings. These I can confirm. Many rovers/mg's appear to have odd fuel guage habbits. Mine personally goes down smoothly to a certain point then drops straight to empty and stays there, very annoying. I once waited a couple of days after this then filled to the brim, only to find there was still 10 litres left in there! Very annoying. While I wouldn't personally drive your car on empty I wouldn't worry too much about it if your car dropped to it, just drive leisurely to the next fuel station. Also you should note that the fuel guages do not tend to read linearly. This means that when your tank shows 1/2, it does not have to be 1/2. It could be 2/3 full, 6/8 full, or anything similar. The top bit of the tank certainly always seems to go fastest. Of course I'm sure you all know that on hills the fuel guage will not be accurate.

Satnav MPG readings. While better than nothing, I certainly wouldn't swear by them. They have no idea of the state of your engine, the size of your engine or anything else. They mainly go by the speed they think you're going and the efficiency you should get at different speeds (you input your urban and extra urban figures). It should also be noted that you should never rely on your satnav speed to be accurate, as they show your horizontal speed only. Because they look at the earth from directly above they can see how fast you appear to be going, but if you are travelling on a hill they will not be accurate, as they do not measure road speed but the time you take to travel between two fixed points on a map (2d, essentially).

Clip-on magnets to improve MPG. I've seen clip on things that "align the molecules in the fuel" to improve MPG. These are utter tosh and not to be bothered with.

Air conditioning / heater blower and it's effect on MPG. Air conditioning or electric heater blowers just like any load on the engine will certainly increase fuel usage, but it should be noted that in proven tests winding down your windows for fresh air actually creates so much drag that it is more efficient to use your air conditioning instead. Good news for anyone travelling in summer I guess

Full tank of fuel affecting MPG. One thing I always used to worry about is that if I filled my tank the extra weight would dent my fuel economy. While this is true, the difference is very tiny. I decided to actually check this and found that 50 litres of fuel only weighs approx 30kg. In a car that weighs well over 1000kgs the difference will be minimal, and nothing to really worry about. Taking on board a lightweight passenger for a journey would damage your fuel economy twice as much as a full tank of petrol does.

Filling your tyres with Nitrogen. This is a relatively new one that I've looked into, the idea being that instead of compressed air, you fill your tyres with compressed nitrogen. The claims are improved MPG and tyre life, as there's no oxygen to corrode the metal. The improved MPG is false, the only reason for this would be that the tyre pressure does not go down as fast due to nitrogen being larger than oxygen, leaking slower. To be honest it's a waste of £4 a tyre asking a garage to fill your tyres with this. Yes, nitrogen leaks out slower than oxygen maybe, but air is 79% nitrogen anyway, so if you pump up your tyres with compressed air as normal and some of the oxygen leaks out you'll end up with a tyre full of nitrogen regardless! As for corrosion, only very small parts of the tyre will be corroded by the oxygen in the tyre if any, as the tyre tread will wear down well before the metal bands do. Also you'd have to take it back and pay every time you want to refil. Personally, I'd rather stick with plain old air.

To finish

Ok guys, I think I've got down as much as I can think of for the time being. I will probably add to this as time goes by, and once my MPG displays are tested and ready to go I hope they can assist you to improve your MPG further!

If you can think of anything to be added here, please let me know

I know it's a long read, but if you do 10,000 miles a year and your mpg improves by just 6% after reading this ( say from 32mpg to 34mpg, a tiny difference ) then you can potentially save 83.65 litres, or £116.27 with today's unleaded fuel prices!

Thanks all :broon:

HJW93 · Mar 21, 2012

Just read through all of this mate and enjoyed it.

As you know I tried some of your tips this evening on an 80 mile round trip from Evesham to Fairford and back and I used less fuel than I do normally. Not only did I achieve a better MPG (don't know exactly but I ended up with more fuel than I normally would from the £15) but I also enjoyed the drive more as I was relaxed and taking the journey at a steady pace.

:broon:

Nice one for this mate.

Roverlike · Mar 21, 2012

Chris,

this is all great stuff you posted here. Thank you for that!

:broon:

chrisoverson · Mar 21, 2012

Thanks guys

.

Joonyer · Mar 21, 2012

This should be stickied imo.

Superb guide.

I strongly second the motorway stuff too - I tend to cruise at 60/65 in the inside lane; it's much more relaxing, you don't have to react to everything at light-speed, and you'll be amazed just how many dodgy near-misses you see from people in the other lanes fighting for position.

Also the difference in mpg from say, 65mph, to 80mph, is absolutely massive over a long journey.

Also as someone who has hit somebody in the back, I can tell you it's a lot less stressful keeping your distance, driving sensibly, and knowing that (touch wood) you are a lot less likely to have an accident.

Matt

chrisoverson · Mar 21, 2012

Thanks mate

. I know what you mean about the relaxation, its amazing how stressful 80mph can be, but 60mph is lovely and relaxing.

Plus you never have to worry about speed cameras, police etc. Much better peace of mind.

iammrarteest · Mar 21, 2012

Awesome guide - think i better change my fuel filter - not sure if its ever been done .
One thing you didn't mention is uneccesary weight in the car - i know most will know this anyway. One think thats always intrigued me is how much difference does it make carrying a space saver compared to a full alloy spare wheel. Is there any forula to work out how extra weight effects mpg - eg carrying one passenger compared to 3 if each weighs an average of 80kg say?

chrisoverson · Mar 21, 2012

Could be done I suppose :lol:. There is a way to calculate the amount of bhp the car must produce in order to maintain a certain speed based upon weight, drag coefficient etc.

I didn't add it mainly because as you say most people will know it, and to be honest short of taking out all your back seats and stripping the car down there's not much you can do that will make any difference. Carrying round a sack of concrete perminantely isn't recommended of course but that's fairly obvious anyway

.

At the end of the day if you get to the point where you have to seriously reduce the weight of your car to increase mpg you need to change cars

.

As for the wheel... I doubt it makes much difference to the weight of the car. Mainly for space and manufacturing costs I would think.

JoshBar · Mar 21, 2012

excellent read, very informative, should help a lot of people.

although on the satnav subject, when travelling at a constant speed, the satnav is correct (have had this confirmed by a friend who's a former test driver, and military vehicle designer). I assume it's something to do with the mapping taking into account the hills, otherwise the distances between locations would be off? But the MPG function on satnavs, is, as you say, ********.

as a fairly open question to people, how does your driving style seem to affect your mpg? in my 200vi, it doesn't seem to make a huge difference whether I drive hard, or gently, I still only seem to get 29-32mpg, which I guess is down to the type of journeys I do? (mainly <15 miles, rural roads, hilly, twisty, junctions). I'll see by next week how being uber-gently helps, as I'm currently being very kind to the car as it's finally got HGF, so driving it carefully until I have a day off on Tuesday to fix it.

psycho_terror · Mar 21, 2012

great guide, and i'm looking forward to seeing those MPG monitors!

Pinkie15 · Mar 21, 2012

Can testify to difference between 60 & 70. My commute is 35 miles, roughly 1/3 Mway, 1/3 dual carriageway and 1/3 single carriageway.

When I first got my Ti I'd drive the Mway/dual at 70 and the single at 60 (if Farmer Palmer wasn't in the way !) I'd get 370 - 390 miles out of a tank (roughly 55l at fill up time).

About 6-7 months ago thought I'd experiment and do the Mway/dual at 60. I can now get 400 - 440 out of a tank.

It maybe added 5 mins to my journey time and I noticed I felt a lot more relaxed when "just bimbling along".

BTW, good write up.

On the subject of Redex, I haven't noticed a change in mpg when using it, but for the first few tanks after using it the car felt more responsive.

Also like the "myth busting" on the full tank argument. Think about it, you've got a tonne+ of car, 10 - 15kg extra of fuel isn't going to make much if any, difference.

One bit missing - Filling up first thing in the morning - are you really getting more for your money ? I don't know if it's true, or not. I do understand the V/D/T "triangle" ('O' level physics useful afterall ??) and how theoretically it could be possible with fuel being sold by volume. But does anyone know for sure ??

Dave_iS · Mar 21, 2012

Pinkie15 said:
One bit missing - Filling up first thing in the morning - are you really getting more for your money ? I don't know if it's true, or not. I do understand the V/D/T "triangle" ('O' level physics useful afterall ??) and how theoretically it could be possible with fuel being sold by volume. But does anyone know for sure ??

Martin Lewis mentioned this bit on the MSE guide, it is true but like other myths only to a certain extent. It doesn't mean you should go out of your way/time to do it.

A great guide, I'll have a better read of it tomorrow but some useful info. I really wish I could get my 25 over 40mpg, I've even stopped driving it around town to get it above 35mpg.

http://www.fuelly.com/driver/daveally/25

v-man · Mar 21, 2012

I had to attend a driver education course last year, one thing they mentioned was that petrol cars give best mpg at approx 2500rpm, which equates to approx 55 to 60 mph in top gear and approx 30mph in 3rd.

D.Ilbert · Mar 22, 2012

You might want to add renewing the oil filter when changing the oil. No point in putting nice clean oil through a dirty filter.

I mention it because there seems to be a belief that it's ok to change the filter every second oil change to save money.

Regards
Dave

chrisoverson · Mar 22, 2012

Updated :broon: thanks! I thought I put it in, must have forgotten.

southcoaststeve · Mar 22, 2012

Really good thread! I'm determined to try some of the techniques to improve efficiency.
I actually changed to the Rover to get better fuel economy, I was driving a 25 year old Audi with an auto box, I was lucky to see mid teen MPG's, but I did like to stomp on the loud pedal to surprise the boy racer idiots!

chrisoverson · Mar 22, 2012

I'd love to get feedback on whether these tips work for people... hopefully they will

I plan on making getting max mpg out of the k-series my current challenge... everybody does fast... I can't afford that so I'll go for saving money instead

.

Dakta · Mar 22, 2012

The key thing is to not only use as little fuel as possible, but get as much out of that fuel as you can.

should be put at the top in bold in size 90 font.

Economy does vary from vehicle to vehicle, but the car is generally as economical as the driver behind the wheel.

Gooner86 · Mar 22, 2012

Awesome work as usual Chris.

Already use most of these techniques (most of the time

) and I can attest they do really work, especially the motorway speeds. I have got upwards of 65mpg (DERV) on long trips on the M6 by sticking between 60-65 and avoiding feathering the throttle as much as possible/drafting behind lorries.

Great write up. Needs to be made a sticky tbf.

Now hurry up and get working on the L-series mpg monitors

chrisoverson · Mar 22, 2012

Thanks

. Most of this stuff is common knowledge and always in the back of our heads when driving, but reading through it or having someone tell it to you helps you become more aware of it when you're driving I find.

Yes I will certainly crack on with the MPG monitors - I would like to see one on a derv, although it'll probably upset me a little after all my hard work to save fuel in a petrol :lol:.

Been working on it a little more this morning, will be posting up some pics and possibly a screen capture of the PC version working later on. The mini-screen is still not finished.

Bren T · Mar 22, 2012

I have just finished reading this and it is quite simply a brilliant thread, it really should be a sticky. I can relate to much of the things you have stated, I try to drive as smoothly as possible, to save fuel and give passengers a better ride. One thing I have learnt is that my fuel filter is probably due a change. :lol:

I actually do have nitrogen filled tyres, but only because I can get it for free, that said it is 1 pound per tyre in my area.

All in all I will take these points into consideration, nice one mate. :broon:

Namonid · Mar 22, 2012

Excellent guide, I mostly follow your advices and now I got a few more great hints, thanks.

Been thinking a lot on fuel economy lately and I finally feel there is a place to ask.

I have an mg zr 160 used as a daily commuter averaging 54mpg.I have a similar style of driving of what you describe, however a few times i do accelerate more then necessary, but I bought the ZR to enjoy it sometimes eventually

My actual concern: My winter tires are on the hairpins(195/55/16), other one on the straights (205/45/17).

I noticed that the straights are heavier than the hairpins by a lot, and also experienced a slight rise in mpg on the winter tires however it is almost the same diameter than the straights (-5mm)

Now I am thinking about putting the summer tyres I had for my VI on the hairpins (205/45/16) . Do you think it could give some noticeable rise in mpg concerning there is a 25mm difference in diameter and again the hairpins are much lighter?

I otherwise know that the ZR accelerates much better with the 205/45/16 wheels, however there is a loss in stability on high speed.

Excuse my english please

chrisoverson · Mar 22, 2012

Anything that speeds the car up without requiring engine modifications means the engine is able to cope better and should in theory increase fuel economy if driven properly.

Wider tyres or low tyre pressure will increase grip and increase fuel consumption, so generally tyres with a little less rolling resistance will improve MPG.

ironeagleuk · Mar 23, 2012

Good guide, and I think I probably follow most of it 99% of the time. Although having said that my biggest problem is not giving myself enough time to get from A-B, and am nearly always late, so alot of the time my MPG goes out the window.

Having said that I do use my Android phone with Torque to keep my MPG in check most of the time. It's great seeing it go to 255mpg when I release the accelerator

If you want to see my Torque Tweets, follow me on Twitter @IEUK_Rover

You can see my current MPG in my sig, and if you click on it, it takes you to the site I use to calculate my MPG

Popeye 89 · Mar 23, 2012

great writeup

loads of good tips there will save people a little money

might want to add something about labouring the engine in there. most people think being in a higher gear is more economical but being at 30 in 5th going uphill labouring the engine is alot less economical than 4th or sometimes even 3rd going up the same hill

chrisoverson · Mar 23, 2012

thanks guys, glad you liked it

Popeye 89 said:
might want to add something about labouring the engine in there. most people think being in a higher gear is more economical but being at 30 in 5th going uphill labouring the engine is alot less economical than 4th or sometimes even 3rd going up the same hill

Yes this is something I'm looking into further using my MPG computer before I write it down. I want to be able to give exact figures for when to change down and when not

. I've found cruising at 30ish on flat / slight downhill in 5th to be very economical, but uphills you're right of course it wouldn't be very good.

Generally it's down to throttle position, the lighter you have to push the pedal the better, and if you have to put more pressure on the throttle in a lower gear then it will often use more fuel. I know the ECU does count other factors but that's the primary one. If it's completely without power then definately change down

.

The Singing Bush · Mar 23, 2012

Fantastic reading that, well done pal and thanks for putting so much effort in

Paulsmitz · Mar 23, 2012

When coasting (rolling downhill with zero throttle), keep revs above 1600RPM (change down if you must) and do not put the clutch down, as the ECU in the K-Series will turn off the fuel injectors and let your engine run on the momentum alone when the RPM is above this point. Do not touch the throttle at all unless you have to, as the second you do fuel will be injected again.

One thing I was wondering as I hate magic numbers... (being a programmer magic numbers are evil)

1600RPM... is this a rover kseries thing or does it map to any car?

how do diesels work with this magic number as they usually rev lower?

chrisoverson · Mar 23, 2012

It's a number that MEMS (the rover engine management system) uses, although almost all modern computer controlled cars will do the same, the exact RPM cut-off point will likely be different.

In the case of our cars they stop injecting fuel if the RPM is anywhere above 1600RPM when the throttle is fully closed (not pushing the pedal at all).

I'm a programmer myself so I understand what you mean xP.

if( engineRPM > 1600 && throttleLevel == 0 ) {
injectorStop();
}

if that helps

Edit: regarding the diesels I don't know as yet, quite possibly yes, as while they rev lower they can still rely upon forward momentum to keep the engine turning without using fuel. The reason the injectors kick in below 1600RPM is to stop the car stalling.

chrisoverson · Mar 30, 2012

Hi guys! Actually had some trouble finding my own thread again as it's not been stickied and had disappeared

.

Anywho, Quick update on a couple of things:

Another technique I'm going to look into is "pulse and glide", mainly good for hybrids but might work for us. Speed up a little, coast till you lose a few mph then repeat.

Also want to examine whether porting and polishing could boost economy a little, as improving the airflow into and out of the heat should theoretically mean the engine has to work that tiny bit less to suck gasses in and get them out. Improves performance too!

A few other bits I'm interested in include leaning out the mixture a little then employing various methods to cool the engine to prevent overheating, such as water injection. Already used on high performance turbo engines but not on production cars.

I've put down all I can think of on regular checks and efficient driving, so now im delving into more interesting methods to get max mpg!

shaunbing · Mar 30, 2012

This could be interesting, isn't porting and polishing quite expensive? So how far would you have to drive before you actually saw a return on your investment?

Also the eco drive may be put on hold if idiots keep stealing all the petrol and not leaving any for me.

Southampton end I should be covered (friend is a manager at a petrol station)

But stoke end I will be stuck, could go for the magic 400 on a tank :O

HJW93 · Mar 30, 2012

Chris, this advice, works a treat! I brimmed my tank yesterday and did 119.2 miles so decided to brim it again, 1 click each time... Only used 11.25 litres which works out at 48.17mpg. Compared to the 35 I've been getting this is one hell of an improvement.

Especially for a 1.6 K-series.

I shall continue driving like this.

chrisoverson · Mar 30, 2012

Fantastic mate, that's very good for a car that has 40mpg extra urban in the book!

Porting and polishing might be expensive if you get it done professionally. I'm thinking of trying it myself as you don't need much equipment. A lot of people consider it for performance reasons anyway, so while your enjoying that you get better fuel economy too, another reason to justify it

.

Thing is with fuel economy you only need tiny differences to make big savings. I spent £3000 one year on fuel... even a 4% difference means £120 saved!

Aden · Mar 30, 2012

Hey Chris, great write up.

Am i thinking you used to have a 211 before the 218?

For a long while now I've believed that the 211 is actually worse for fuel economy that probably some of the others in the range due to its close ratio gearbox relative to the others.

I know someone else earlier mentioned at 2.5k rpm is most efficient for the engine and I have done several long journeys at 2.5k rpm, 3k rpm, and so on (500rpm increments) upto just over 4.5k rpm.

The issue in my opinion with the 211 is the speed in 5th gear typically equates to 20mph per 1k rpm... which means the 2.5k rpm sweet spot leaves you plodding along at 50mph... useful if you want economy but not great when lorries are overtaking you.

I was wondering if it is something you'd noticed yourself? And how the fuel economy compares at say 70mph in a 218 and a 211... due to the difference in both engine capacity and also gearbox ratios.

My 211 is certainly a guzzler above 70mph as you end up pulling 3.5k-4.5k rpm to stick with the flow of outside lane (not that anyone is forced to - just wondering how it'd compare with a larger capacity engine).

I'm pretty sure the BRM has a close ratio gearbox too and some fit them to their ZR's etc - I'm sure its a way of denting mpg figures... but then those who are doing those sorts of upgrades are probably going for power not economy

Again, great right up!

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How-to: Get Better MPG out of your Rover or MG!

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