[Chindley]

O.k Im might be asking a silly question but here goes.
If i'm travelling at 35 mph would it be more economical to use 5th gear at lower revs or stay in 4th?. Reason i'm asking is that I saw an article saying that your car uses more fuel coasting down a hill(i.e clutch dipped) than it does keeping it in gear.

 

[Big Al]

Regarding which gear to be in going downthe hill, 5th would be the most economical. Regarding stopping in gear or dipping the clutch is debatable if you stop in gear the fuel shuts off and the momentum of the car keeps the engine turning, if you dip the clutch fuel is used to keep the engine turning the only disadvantage to keeping it in gear and using no fuel is that by keeping it in gear the gears slow you down and youhave to return to the accelerator sooner using fuel that you have just saved. so its up to you whichis most economical, or is it negligible.Don't forget with a penny off a litre its flat out all the way now for me.

 

[K.L.Richards]

I've heard this before and don't dispute it, it sounds mechanically sound.... <?: prefix = o ns = "urn:schemas-microsoft-comfficeffice" />

BUT... How do you actually stop a car without dipping the clutch? In the numerous years I've been driving, I can safely say doing this stalls the car.

Now, before anyone says put it into neutral, I'd like to point out that doing that means the engine is "disengaged" from the gear box hence the drive, and hence has to use fuel to keep running, same as "dipping the clutch".

So can someone please explain this fantastic method of stopping without using fuel?

Jeremy Clarkson stated this on Top Gear, but never explained how. Wouldn't be surprised if it is total Clarkson b****ks.

It's like these "new" engines that stop when the car is stopped to save fuel. The trouble is they have to be restarted, and although this is done through computer as soon as you put your foot on the accelerator, it takes more fuel to start the car than the amount saved if you just let it run in idle for the brief moment at the traffic lights or junction in the first place.

 

[Chindley]

What I meant was, if you are going down a hill, rather than just easing off the accelerator I usually dip the clutch to manage my speed (especially on that steep hill on the A55 in North Wales!!) but the same could be said when approaching a junction, I usually take it out of gear and coast to the junction, where I should probably be using the gears to reduce my speed because a car idling is using fuel where if it's in gear and slowing down it's not. I'm probably over thinking the whole thing.

 

[K.L.Richards]

Ahhh... now that makes perfect sense.


And yes you should be using your gears, as to put it into neutral or "ride the clutch" is actually a driving offence as the car is free wheeling and hence technically out of control.



Years ago I was pulled in for the same thing on Thornhill (South Wales going down hill to Caerphilly). I had the car in neutral just free wheeling applying the brake now and again, and next thing a blue light behind me. PC Plod, tokld me that free wheeling was an offence as the car in not under the driver's control. Being very young I didnt argue, and after he kept me for 30 mins, checking the car over and making me feel really guilty, he "let me go" with a warning "this time".