Freewheeling to save money

Trazy

I was talking to a friend and he said he free wheels to save money whenever he can and when it is safe to do so.

It got me thinking, does anybody else do this and does it really save any money? Also, what about the safety aspect?

Bongles

Do you mean freewheeling as in rolling along in neutral (or with the clutch down)?

Leaving aside for a moment any issues of safety, control or legality, doing that will use more fuel than staying in gear with your foot off the gas so it doesn't exactly score well on the money saving scale.

Or have I misunderstood what you're on about?

reeac

Trazy wrote: »

I was talking to a friend and he said he free wheels to save money whenever he can and when it is safe to do so.

It got me thinking, does anybody else do this and does it really save any money? Also, what about the safety aspect?

I understand that modern cars feature complete fuel shutoff when there is no pressure on the accelerator as long as the road speed is above a certain level - probably as long as the engine speed is at or above idling speed. Thus zero fuel consumption on overrun if in gear but some fuel consumption [equivalent to idling level] if in gear. Thus no fuel saving by freewheeling.

DigForVictory

This came up on one of my police driving lessons (the sort that you sometimes are offered as an alternative to points).
Just Don't.
You are not "in control of your vehicle", and they take a very dim view of it.

Trazy

The car is pretty old so I don't think it has the cut off thing.

I think he meant rolling in neutral.

Thanks for all your replies, I can now go back with a bit of knowledge

reeac

reeac wrote: »

I understand that modern cars feature complete fuel shutoff when there is no pressure on the accelerator as long as the road speed is above a certain level - probably as long as the engine speed is at or above idling speed. Thus zero fuel consumption on overrun if in gear but some fuel consumption [equivalent to idling level] if in gear. Thus no fuel saving by freewheeling.

Slight error there! I intended to say "[equivalent to idling level] if freewheeling".

MickMack

Bongles wrote: »

Do you mean freewheeling as in rolling along in neutral (or with the clutch down)?

Leaving aside for a moment any issues of safety, control or legality, doing that will use more fuel than staying in gear with your foot off the gas so it doesn't exactly score well on the money saving scale.

Or have I misunderstood what you're on about?

How exactly does coasting along with your foot on the clutch, and thus the engine idling load free, use more fuel than driving along with the car in gear and thus the engine under load?

Obviously it's a silly thing to do from a safety point of view and i would suspect that the fuel 'saving' would be marginal if any, it sounds like someone whose kidding themselves!
I think adopting a more fuel efficient driving style might be of more benefit

mad_rich

MickMack wrote: »

How exactly does coasting along with your foot on the clutch, and thus the engine idling load free, use more fuel than driving along with the car in gear and thus the engine under load?

Because the engine needs to turn at ~1000 rpm to idle.

If the car is in neutral (or the clutch is down) it does this by merrily combusting and using fuel.

If you are in gear, with your feet off all the pedals, the road wheels are turning the engine via the transmission, hence no fuel is needed.

The downside is that you'll have engine braking, so your run will be shorter than if you were out of gear.

Herzlos

MickMack wrote: »

How exactly does coasting along with your foot on the clutch, and thus the engine idling load free, use more fuel than driving along with the car in gear and thus the engine under load?

Because the momentum can keep the engine turning over without injecting more fuel. If you've got the clutch in, it needs to provide fuel to idle. The differences are minimal, but there's still zero benefit in coasting out of gear.

OddballJamie

I hope all this money your friend is saving is being put aside for new pads/drums for the extra braking involved. Also do it too much on a few steep hills and he will start to experience brake fade from the excessive use.

Iceweasel

Also - if he's coasting with the car in gear and his foot on the clutch pedal, expect to have to replace the clutch release bearing early, as it's not designed for such prolonged use.

Same as sitting at lights with foot on the clutch instead of engaging neutral.

Very bad practise - not mechanically sympathetic and saves nothing - quite the opposite in fact, in the long run.