Martin's 10 ways to save fuel advice

Scarlett25

This was in today's Sun newspaper by Martin:

1 - Only use your car if it's necessary. If the destination is close by, walk or bike it.

2 - Keep your car well maintained. A poorly tuned engine can up fuel consumption by a massive 50 per cent.

3 - Plan your journey. According to the RAC, British drivers waste the equivalent of 267 Olympic swimming pools of fuel going the wrong way.

4 - Remove unused roof racks. Due to the extra drag, they increase fuel consumption by up to two per cent on the motorway.

5 - Fill up early morning or late at night when it's cooler because fuel is denser then and you'll get more into the tank. The difference may be pennies, but it all helps.

6 - Check tyres are properly inflated. Under-inflated tyres can reduce fuel efficiency by up to three per cent.

7 - Don't use air conditioning. It increases fuel consumption by 8 per cent.

8 - Drive at 56 mph. This is the most fuel-efficient speed. Slowing down to 56mph from 70mph will cut fuel consumption by 20 per cent.

9 - Don't accelerate quickly then brake hard at the next traffic lights. By raising speed gradually and paying attention to traffic conditions, you'll increase fuel efficiency by up to 20%

10 - The lighter your car, the less effort is needed to accelerate. So clear junk from the boot and avoid carrying unnecessary weight. Fuel efficiency can rise by up to 2%

Hintza

A couple of issues:-

7. Not convinced that Aircon has that much effect on modern cars (it will still affect though). Of course the effect will be higher on smaller less powerful cars and I suppose could be around that figure.

8. 56mph will not necessarily be most fuel efficient and more to the point will cause huge problems with trucks on the motorway. A speedo reading 56mph means you are probably travelling at +/- 52 mph. By all means slow down but sticking to +60mph would be better.

tomstickland

5
5) the fuel will be more dense, but the tank and the pumps will also have contracted.

9) Don't accelerate and then brake heavily. Yes. However, gentle acceleration is less efficient than reasonably hard acceleration. So, it's most efficient to accelerate reasonably hard, but only for a short while, and then let the car run on overun to the obstruction. Or if there's no obstruction, a short burst of reasonably hard acceleration is more efficicent than long, gradual acceleration.

steveo3002

that 56mph one....must vary wildly on what car and what gearing the car has, surley youd want to work out at what revs the engine makes peak torque and drive around that?

AdrianHi

As other research had found:

7. In my opinion a dangerous suggestion in a hot summer and not true if it is automatic air conditioning (climate control) where the impact on fuel consumption is so small you can't measure it out on the road. On the open road opening the windows increases drag and puts you back to where you were on fuel consumption even with manual air con. The best bet is to use air con. to be comfortable but not have it running unnecessarily. If you have auto air con you dial in a temperature and leave it on all the time - it automatically comes on as needed.

8. This one is very inaccurate, the fuel use by speed is very dependant on the car. A sweeping generalisation like 20% cannot be made. Driving at 56mph may create an obstruction and reduce the effective capacity of the road - creating congestion and increasing fuel use for everyone else. It's much more important to drive with the flow at a speed safe for the conditions and within legal limits.

11. Not on the list but it probably should be - if possible avoid driving at times of congestion, thus reducing your journey time and the length of time the car is actually running. Saving up to ... well that would depend on the route, I can save around 10% on the mpg across a tank full in school holidays with no school run traffic causing congestion.

daveonline

Any thoughts on using cruise control - increase/decrease fuel consumption ?

AdrianHi

daveonline wrote: »

Any thoughts on using cruise control - increase/decrease fuel consumption ?

Tricky one. Depends on conditions.
If you have conditions where you are able to put CC on and leave it on for a long period and you have a reasonably flat road (not too many steep hills) CC can save you a little simply because the computer is better than a person at keeping a consistent accelerator input. A person will be fidgeting and increasing accelerator input when not necessary for maintaining speed and even give a higher accelerator input than needed to maintain speed but not enough to increase speed. I've observed this effect on my car as it has an instantaneous MPG meter and the difference can be as much as 5mpg on my diesel car, that's about a 10% saving (which does not mean an overall 10% saving in fuel use of course! .. just for the period where this difference occurrs).

On a busy road where you would need to keep cancelling and re-engaging CC the most systems do not have a brain or eyes so may accelerate you to too high a speed for the traffic in front and you'll be cancelling and hitting the brakes again. Not a good CC situation unless you have one of those more advanced systems which can detect distance to the car in front and adapt accordingly.
Also if you get steep hill's the CC will whack on the power to maintain speed up the hills and overshoot on the way down possibly causing you to break to keep your speed inside limits. This is wasteful. If you drive the hill your self you can let speed bleed off up hill (probably in step with other traffic) and then use the downhill stretch to help you up to cruising speed again which is more efficient.

tomstickland

steveo3002 wrote: »

that 56mph one....must vary wildly on what car and what gearing the car has, surley youd want to work out at what revs the engine makes peak torque and drive around that?

Peak efficiency and peak torque don't have to be at the same rpm. Peak efficiency is more rpm related. Low rpm provides poor filling efficiency and high rpm introduces high frictional losses, so peak efficiency tends to be in the middle, slightly towards low rpm.

jaydeeuk1

AdrianHi wrote: »

Tricky one. Depends on conditions.
If you have conditions where you are able to put CC on and leave it on for a long period and you have a reasonably flat road (not too many steep hills) CC can save you a little simply because the computer is better than a person at keeping a consistent accelerator input. A person will be fidgeting and increasing accelerator input when not necessary for maintaining speed and even give a higher accelerator input than needed to maintain speed but not enough to increase speed. I've observed this effect on my car as it has an instantaneous MPG meter and the difference can be as much as 5mpg on my diesel car, that's about a 10% saving (which does not mean an overall 10% saving in fuel use of course! .. just for the period where this difference occurrs).

On a busy road where you would need to keep cancelling and re-engaging CC the most systems do not have a brain or eyes so may accelerate you to too high a speed for the traffic in front and you'll be cancelling and hitting the brakes again. Not a good CC situation unless you have one of those more advanced systems which can detect distance to the car in front and adapt accordingly.
Also if you get steep hill's the CC will whack on the power to maintain speed up the hills and overshoot on the way down possibly causing you to break to keep your speed inside limits. This is wasteful. If you drive the hill your self you can let speed bleed off up hill (probably in step with other traffic) and then use the downhill stretch to help you up to cruising speed again which is more efficient.

If you ever saw the top gear episode where Clarkson drove an A8 diesel from London to scotland and back on one tank showed he got improved MPG with the cruise control off...

AdrianHi

jaydeeuk1 wrote: »

If you ever saw the top gear episode where Clarkson drove an A8 diesel from London to scotland and back on one tank showed he got improved MPG with the cruise control off...

Did he do the whole round trip using cruise and the then whole round trip again in the same weather conditions and same speed with the cruise off?
What other variables could there have been?

I'm in communication with someone on a car enthusiast forum who lives in the highlands and often travels to Wiltshire. He's been doing it for years. He always gets better MPG coming south compared to going north and he has observed this on more than one car.
We even half jokingly wonder if coming south is more economical because on average your going down hill :rotfl:

daveonline

Comprehensive reply - thanks AdrianHi, will try it with/without on the route i use.