When coasting down a hill for MPG, is it better to A) take the car out of gear (releasing driveline friction) but injectors are squirting gas to keep the car idling or B) leave the car in gear and squirt no gas but driveline friction is in effect?

(I would think B is better, but not sure if indeed the car's injectors shut off while coasting in gear.)

 

I'd say taking it out of gear, since driveline friction would slow the car and you'd actually be going down the hill slower than if you were just coasting in neutral, but coasting in neutral is illegal I think. Or atleast I read it on a sign here in Nevada. I'm guessing since you have less control over the car technically since it isn't in gear for you to accelerate if need be. Sorry for going OT.

 

you would probably use more gas staying in gear. i almost always coast when i can, sometimes thats for a half mile or so

 

Yes, the injectors cut off when you decelerate in gear. However, if you aren't planning to stop, a neutral coast down hill would likely save gas. If you are coming to a stop, stay in gear.

 

I don't think it's ever wise to take a car out of gear while in motion. I know there are different schools of thought on this however that's my 2c. You do not use fuel while decelerating under gear.

 

Its called engine braking. Its when you leave the car in gear and you are off the gas compleatly. During this time you are not using a drop of gas. So if you do this down a hill I would put it in the highest gear so it doesnt slow the car down to much. If you need to go the put it into the proper gear and go. Make sense?

 

I believe in gear would be better since it's not burning gas.

the best of all (but stupid) would be to cut the engine and coast in neutral. but since you can afford an evo you shouldn't be caring about saving .04 cents

 

i prefer going down a hill in neutral.
cheaper to replace worn brakes than a worn clutch.

EDIT: plus your car idles at a lower rpm than coasting most of the time- less rpm, less wear in the cylinders, cams, and crankshaft

 

Thanks for thinking for me sweetcakes, I'll take it from here.


Thx for everyone's reply, IGO4BMA, good point. Using some gas while coasting as opposed to driveline wear is a fair trade-off.

 

technically its illegal in most states. to be coasting in neutral.
one of those laws most people dont know about.

i never heard of it till it came up in a discussion.

and to iq04bmx lol your not going to wear your clutch be being in gear going down a hill.

 

I remember getting yelled at on my driving test for not being in gear at all times....eh. *shrugs*

And no the clutch won't wear I don't believe, but the rest of the driveline is engaged when coasting in gear, so I'll coast out of gear I think.

 

i always take mine out of gear. or when im passing a cop on the side of the road i do the same : )

 

so what happens when the guy in the other lane sudenly pulls toward you or if you had to accelerate to get out of a almost accident?
you are screwed.

its always best when driving a manual car to be in the correct gear no matter what.

 

I don't coast down large hills in heavy traffic, often times it's on desolate highways when traveling to and from my parents. I would not do it when there are too many other cars around as often u have to brake for the car in front of you as you accelerate anyway.

 

this topic is pretty trivial but i admit i think about this too (for ****s and giggles)... try coasting down a hill in gear and see how it slows you down. even if your in top gear, theres still measurable amount of engine braking and friction from the powertrain slowing you down. i see very often even in my 2wd civic i can coast MUCH further in neutral then in gear so i think the few drops of fuel i used to keep idling was much better used.