I don't know the answer, but it might be possible for it to be nearly equal. I'm just guessing but if the ECU knows that the rear wheels are driving the engine it could decrease fuel flow to the lowest level required to maintain ignition. Just a guess.

 

As long as your car is in gear, the RPM's are above a certain point(1500 RPM's), and you have your foot completely off the gas with the engine fully warmed up... the fuel cut feature will engage as you coast for a second or so. It's called DCFC(Deceleration Fuel Cut) in most vehicles, and it's not new technology. It's been around for at least 10-12 or more years on many cars and you use no fuel when it's in effect instead of using the amount of fuel that is required to idle(which is what you use when you put it in neutral while coasting down a hill or to a stop light in neutral).

You can read about it in the FSM... it's on page EC-28 and is described as Fuel Cut Control(at no load or high engine speed) on our cars.

Moral of the story.... leave it in gear, it's more efficient and helps reduce wear on your brake pads as engine braking will slightly slow the car down, and prevent it from accelerating while coasting down a hill. It's also good from a safety standpoint too, in case your car were to stall while coasting in neutral... if you're in neutral, you would lose your power steering and brake assist... if you're in gear, your motor is turning regardless of whether or not there is ignition, so the power steering pump and master cylinder will continue to function.

 

[QUOTE=scrapiron7;5462700]That's like saying the car uses more fuel at idle then higher rpms...

So coasting in Neutral at 800 RPMS uses more fuel than decelerating at 2300 RPMS?

[/QUOTE

yes, if your in higher rpms in gear most likely your foots on the gas. as soon as your not giving the engine any throttle, it cuts all gas to the engine until about 1.5 rpms to keep the engine from stalling

 

i would much rather put wear on replaceable inexpensive brake pads then put wear on my engine components... i throw it in neutral

 

the real question is do you want to leave it in gear and put more wear on your engine and save gas?

or do you want to throw it in neutral to reduce engine wear but use more gas ?

 

The engine wear you guys are worrying about is negligable. Even over the life of the car. You're more likely to add wear to the throw out bearing by coasting with the clutch in. If you clutch then put it into neutral and then coast then you're adding unneccessary wear to the clutch and the throwout bearing. Again, I think folks are overthinking this. In reality it makes little difference how you do it but I wouldn't assume that any of these ways makes any measurable difference in mileage or wear and tear.....at least on the engine. I'd be more worried about my left knee.

 

Keep it in gear until you start bogging.

When coasting in gear your engine effectively becomes a giant air compressor driven by the inertia of the car; combustion does not happen. It actually saves wear on your engine, injectors, etc.

I personally do it all the time, even rev match downshifting to the point where I can coast to an almost stand still (Usually second gear)
My neighborhood has a lot of steep hills, old people, and a low speed limit. I can stay in second gear off the gas and stay at the limit, keeping the geezers off my back.

 

thank you to everyone!!

 

I shift to neutral and use the brakes when needed. Most of the time, the light turns green before I have to apply the brakes.

Stop and go traffic, I rarely ever use the brakes. And people complain about driving a manual in traffic?

 

Keep in gear in case you need to give it some gas for emergency instances...
I always find leaving in neutral creating a lag for emergency reactions.
i.e. imagine you have to dodge something as you slow down to 10mph ish...

 

It really doesn't help much, I always do because its just habbit, but its not going to save you much on gas. I currently get 18 with a mix of highway and city - i've been in a hurry at some points in time though. Just try and drive smooth.

 

There is an insignificant engine wear difference by doing this compared to just idling in neutral. The engine is just being pulled by the cars momentum at about 2500 or so RPM with no combustion going on in the cylinders while coasting in gear, compared to the engine spinning at 1000 RPM and combustion going on in the cylinders.

 

I agree with this. Leave it in gear, let the fuel cut off do its job, and worry about saving fuel in other ways like more gradual starts, anticipating stops or slow traffic ahead and getting out of the throttle, and incorporating multiple stops in one trip instead of making several short trips.

 

^^^ this is a good way to think of it… i might actually start leaving it in gear more often.

 

I always put mine in neutral when stopping (completely) IE stop sign, Red Light. Brake pads are a lot cheaper than clutches. Sometimes i downshift but really it makes no difference, all your parts are going to wear out eventually. Gas savings would be a wash either way, i highly doubt you would ever notice a difference over a month period of doing downshifts vs neutral stops. The only time i leave my car in gear is when i dont have to come to a complete stop.