Which uses more fuel........

[John V]

In my brain it still seems more logical that a car uses less fuel while coasting at idle than it does in gear. I mean, if you check any of the hypermiler websites, they always emphasis coasting as much as possible to increase fuel efficiency.

But this discussion obviously pertains to coming down gentle/occasional slopes, not coming down a mountain in New Mexico/Colorado as I would never attempt that coasting.

It depends on too many factors. If the hill is sufficiently steep that the car can hold a given MPH with engine braking, the car will use less fuel than if you push in the clutch and let the engine idle. The engine uses no fuel when engine braking. It uses fuel when idling. Period.

[JeTexas]

In my brain it still seems more logical that a car uses less fuel while coasting at idle than it does in gear. I mean, if you check any of the hypermiler websites, they always emphasis coasting as much as possible to increase fuel efficiency.

But this discussion obviously pertains to coming down gentle/occasional slopes, not coming down a mountain in New Mexico/Colorado as I would never attempt that coasting.

It depends on too many factors. If the hill is sufficiently steep that the car can hold a given MPH with engine braking, the car will use less fuel than if you push in the clutch and let the engine idle. The engine uses no fuel when engine braking. It uses fuel when idling. Period.

I guess the real point the hypermilers are always trying to make is that if you plan ahead and COAST TO A STOP instead of braking at the last minute, you save gas.

[John V]

In my brain it still seems more logical that a car uses less fuel while coasting at idle than it does in gear. I mean, if you check any of the hypermiler websites, they always emphasis coasting as much as possible to increase fuel efficiency.

But this discussion obviously pertains to coming down gentle/occasional slopes, not coming down a mountain in New Mexico/Colorado as I would never attempt that coasting.

It depends on too many factors. If the hill is sufficiently steep that the car can hold a given MPH with engine braking, the car will use less fuel than if you push in the clutch and let the engine idle. The engine uses no fuel when engine braking. It uses fuel when idling. Period.

I guess the real point the hypermilers are always trying to make is that if you plan ahead and COAST TO A STOP instead of braking at the last minute, you save gas.

Yes but remember they are not coasting with the engine idling, they are shutting the engine OFF. The idea is that you're not wasting any inertia.

The original poster didn't say anything about turning the engine off and presumably he's not letting the car pick up speed so that it's exceeding any safe speed limit.

[Panzerkampfwagon]

In my brain it still seems more logical that a car uses less fuel while coasting at idle than it does in gear. I mean, if you check any of the hypermiler websites, they always emphasis coasting as much as possible to increase fuel efficiency.

But this discussion obviously pertains to coming down gentle/occasional slopes, not coming down a mountain in New Mexico/Colorado as I would never attempt that coasting.

It depends on too many factors. If the hill is sufficiently steep that the car can hold a given MPH with engine braking, the car will use less fuel than if you push in the clutch and let the engine idle. The engine uses no fuel when engine braking. It uses fuel when idling. Period.

I guess the real point the hypermilers are always trying to make is that if you plan ahead and COAST TO A STOP instead of braking at the last minute, you save gas.

Yes but remember they are not coasting with the engine idling, they are shutting the engine OFF. The idea is that you're not wasting any inertia.

The original poster didn't say anything about turning the engine off and presumably he's not letting the car pick up speed so that it's exceeding any safe speed limit.

Not to mention, the steering wheel lock might activate if the car is turned off?!?! Guess you'd better leave it in ACC whiles you're coasting 80mph downhill with no engine braking - so you can listen to the stereo, right? :rolleyes:

[John V]

Not to mention, the steering wheel lock might activate if the car is turned off?!?! Guess you'd better leave it in ACC whiles you're coasting 80mph downhill with no engine braking - so you can listen to the stereo, right? :rolleyes:

I don't think any of us are suggesting that this is a good idea.