Fuel consumption

[Willienelson]

I've seen quite a few threads on here about consumption and some have said that they coast (ie in neutral) whenever they can.
It's worth pointing out that when you are coasting the engine is actually using fuel to keep the engine running, whereas if you don't 'coast' the engine is actually more economical.
Sounds strange I know but give it a try it may help.

[ColinW]

Originally Posted by Katpee

I've seen quite a few threads on here about consumption and some have said that they coast (ie in neutral) whenever they can.
It's worth pointing out that when you are coasting the engine is actually using fuel to keep the engine running, whereas if you don't 'coast' the engine is actually more economical.
Sounds strange I know but give it a try it may help.

Sorry, not true in an auto. The engine has to overcome the frictional losses in the torque coverter even if the foot is off the gas. The ECU maintains the same idle speed, whatever the load. So that at idle, in gear, whether you are coasting or not, the ECU has to overcom the extra load. When in neutral, the ECU sees less load, so that it uses less fuel. For sure it may be marginal, but all these marginal increases do add up.

That's why I generaly go into neutral at lights, or waiting in traffic. Sure it's using fuel, but just a little bit less.

I hope this is understandable

Colin

[David3807]

I guess thats why the handbook suggests moving an auto to neutral if you are going to be stopped at say traffic lights for more than 15 seconds.

[Simondi]

Anywhere I look there seems to be a huge debate over how to drive most economicaly.
I've alwys tried to be gentle on the throttle and avoid foot to the floor however I read recently that the engine runs more efficently when the acceleraor is used like an on/off switch (only up to appox 2000rpm). Therefore, apparantley when driving around town instead of keeping a constant revs and having accelerator always slightly depressed it uses less fuel to take the foot off the pedal and when speed drops floor it up to 2000rpm and then either change gear or take the foot off again.
I guess the thought is that constant use of accelerator uses more fuel than occaisional heavey use.
Good fun though

[Zeb]

Is it actually legal to coast in neutral? Or are you technically not in full control of the vehicle? Always wondered about this!

[JP53]

During the fuel blockade I was driving an MGC GT. 3 litre engine, balanced high lift cam, balanced lightened fly wheel etc, in those days my attitude to (high fuel consumption was stick another carb on it), she sounder great BUT I was lucky to get 12 MPG. However, coasting, changing up earlier and doing a lot of praying I managed to get a tank of fuel to last until supplies got through. I got my MPG up to nearly 25!!!!

I think it is illegal to coast Zeb, however one could always state that it was being done for the good of the environment!

[5000SE]

Originally Posted by Katpee

I've seen quite a few threads on here about consumption and some have said that they coast (ie in neutral) whenever they can.
It's worth pointing out that when you are coasting the engine is actually using fuel to keep the engine running, whereas if you don't 'coast' the engine is actually more economical.
Sounds strange I know but give it a try it may help.

Fuel is still fed to the engine if you coast in gear - more than if you let it slip to neutral and idle.
Try zeroing your trip computer fuel consumption reading as you coast down a hill in gear, and see what figure it steadies at and gives you. Then zero it again after you put her in neutral and see what that gives. The former might be 70mpg, the latter could be 200 or more.
I have a 55 mile A-road drive into work every day, and I experiment to relieve the boredom. Driving gently and deliberately aiming for economy in gear, I can get a bit over 50mpg. By coasting in neutral at every opportunity, I’ve had it up to 56mpg, always over 54, and don’t worry about the safety issue of potential wheel lock up in neutral because of the ABS.

[Mike]

My (very) old BMW 325i has an econometer on the instrument panel - it's like a pendulum that swings right to left indicating current consumption measured on a scale. Driving by it does show that sharp on/off loud pedal movements are the most economic, i.e. get up to speed as rapidly as possible and then cruise. Mind you, who'd ever trust BMW electronics eh

My 75 2.5 KV6 is fitted with something similar - there is a gauge on the rh side of the panel that plummets rapidly when I put foot to floor. I'm yet to find a way of getting it to swing the other way.

[CFS75]

I remember back in the 1960s that a friend had a Rover with some sort of 'freewheeling' device. When you took your foot off the accelerator the car carried on coasting or freewheeling, the idea was to improve fuel economy.
I drove it on one occasion and it was an extremely frightening experience because the car did not slow down until you braked.
It must have been legal at that time because it was standard equipment.
Does anyone else remember this device or is my memory going?

[JP53]

Originally Posted by Mike

My (very) old BMW 325i has an econometer on the instrument panel - it's like a pendulum that swings right to left indicating current consumption measured on a scale. Driving by it does show that sharp on/off loud pedal movements are the most economic, i.e. get up to speed as rapidly as possible and then cruise. Mind you, who'd ever trust BMW electronics eh

My 75 2.5 KV6 is fitted with something similar - there is a gauge on the rh side of the panel that plummets rapidly when I put foot to floor. I'm yet to find a way of getting it to swing the other way.

Try turning it up the other way, otherwise...........NO.