Driving 30mph in 5th gear

[DC_FC]

I always thought driving at a low speed eg 30 in 5th gear would use more petrol than driving in 4th gear as the engine has to work harder, have i been wrong all these years and been wasting petrol,

[Answerprancer]

This site should give you some interesting facts re your question :-)
http://www.hypermiling.com/

[Toureman]

Yes and no depends how you do it and it depends on what sort of car you drive.

I have a 1.8 ltr large family petrol car, I often drive at 30mph in 5th gear when on a level road but I do not try to accelarate or go up hill in 5th gear at that speed as that would make the mpg rocket up as you would need to put your foot down quite hard making the engine struggle and waste a lot of petrol I would drop to 4th or even 3rd which is more economical.

The most economical speed for my car is to do 45mph in 5th.

I get 39mpg overall.

[Hopkirk]

There is another consideration.

You are more likely to brake the speed limit if you select too high a gear for the speed.

It is probably more sensible to use 4th.

[Hopkirk]

Sorry, ......break the speed limit...

[The-HouseHusband]

If you are driving a modern car then driving in any gear and keeping the engine revs constant will use fuel. It is actually more efficient to accelerate and then coast with the vehicle in gear as modern fuel systems shut off the fuel flow on overrun as the momentum of the car keeps the engine turning without the need for fuel. I realise this may seem against all that has been said before in magazines and the like but it is a proven fact.

[alavahalf]

Think I must have followed you on my way home tonight as you accelerated to 30mph and then slowed down for no apparent reason.
Sorry if the police breathalysed you..!