Coast in-neutral vs in-gear: I've been challenged to show the numbers

[Xist]

Originally Posted by undata

Unless you're sharing a car with person(s) incapable of learning to drive a manual, why not just get a manual transmission?

Heh. Incapable of learning. If they cannot learn, should they be driving at all? One of my friends says that she could not get her permit because she gets test anxiety.

I am glad that she is not on the road.

My mom used to enjoy driving my Prelude, but she has arthritis. My dad bought the automatic Focus SFE for its 5% improved mileage (for about five percent more money).

I bought my first automatic simply because I could not find a good manual.

It is not an ideal world.

[Fat Charlie]

We hadn't owned an auto since 93, but what we got earlier this year doesn't offer a manual. Sometimes the platform is more important than the transmission.

[undata]

Driving habits probably trump even transmission type. In the Wash. D.C. area, where many people have the money to get that nice Prius, I can't tell you how many times I've seen people driving them like complete lunatics. And I mean complete raving drooling idiots. It's one thing to be out of it (some very old drivers) but these people skew younger, they just have no concept whatsoever of how to conserve fuel or the machine they are operating.

[Arragonis]

I know the original post is OLD but there is no answer. If you start your journey at the top of a hill and end it at the bottom, then in gear wins because of the fuel shut off.

If you start at the top of a small hill and end at the bottom then out of gear wins because you coast for longer and use your throttle less. In this case (if you want to) then engine off coasting wins more.

Why is this a one or the other debate ?

Use which one suits your immediate circumstances, in fact use both if it works for you.

[Gealii]

looking back it is all in the situation your in i believe not all cars have dfco and some autos automatically switch into neutral while in gear when the the gas pedal is released. Its important to just do testing and research with your car and find whats the best.

[Arragonis]

+1 - there is no correct answer, there are no hard numbers to show. Either is better than just shoving it.

[Gasninja79]

I did notice an uptick in my MPG when starting to coast in Neutral vs. normal braking. from 33.2 to 37.8 mpg.

Does anyone know, mechanically speaking, if switching between drive and neutral on an automatic transmission is harmful to the transmission?

[Gealii]

Originally Posted by Gasninja79

I did notice an uptick in my MPG when starting to coast in Neutral vs. normal braking. from 33.2 to 37.8 mpg.

Does anyone know, mechanically speaking, if switching between drive and neutral on an automatic transmission is harmful to the transmission?

Read in your owners manual how your car should be towed. I know for a fact that in auto tranny jeeps it is very harmful to coast in neutral as the trannys stop getting oil and burn up. other than special cases if neutral was bad for trannys to be placed into it would be like reverse very hard to get into when moving forward with speed

[PaleMelanesian]

That applies to engine off coasting. As long as the engine is running, the transmission should be lubricated by an engine-driven pump. In all but a handful of cases (maybe the above-mentioned jeep?), neutral with the engine on is just fine. It's engine-off that you need to check the manual for towing instructions.

[ctgottapee]

how about this...

In my '93 Caddy, I have a real time gas gauge (injector pulses / wheel revolutions)
-if i coast in gear, I don't have fuel cut off, so while the engine might be braking, it is still using some fuel at the in gear lower rpm, and comes down through the gears at lower rpm

-if i cost in neutral, the rpms jump up [probably so there is torque when dropped back into gear ] so i'm still burning fuel in neutral, possibly more and it is not going to the wheels

-note: if i EOC by turning the key, i'll often get a smell of gas upon startup. and with the computer not liking the power off, nor any injector pulses, mileage is tough to compare


The instant gas gauge reports similar fuel usage and sometime more usage in neutral, but the gauge doesn't let me measure averages for a couples minutes of coasting very easily