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

[Fat Charlie]

I did a big trip this summer pulling a camper, and with the cruise on the transmission downshifted on downhills to try to keep the speed down! I haven't owned an auto in almost 20 years, but that really shocked me.

I fixed it by canceling the cruise on big downhills.

[Xist]

I once talked to a girl that mentioned her cruise control applying brake going down a hill. She had a 1999 Civic. Maybe if I had a newer car it would do the same thing.

And I would yell at it!

That helps.

[ecomodded]

Originally Posted by UltArc

I haven't been too up to date on here, and this thread is old, but coasting today in my wife's 2008 Ford Escape 4 cylinder auto had roughly a 25% loss in efficiency by putting it in neutral. It went from 80s to 60s. Watching more carefully, rpm went from 900ish to over 1200 in neutral.

Its like that car has it backwards?
It has a high rpm, well seems high to me, my car has a 850 rpm neutral idle and 1000 rpm at cruise.
Wow, big numbers you are getting, are the figures 80 to 60's with the scangauge or at the pump?

[PaleMelanesian]

The F150 Ecoboost does that. Shift into neutral and it holds the rpm at 1200. Not much point.

[TheIVJackal]

Originally Posted by PaleMelanesian

I think you're looking at it backwards. Don't look for the perfect place TO coast, look for the special cases where you should NOT coast. In other words, make coasting your default, and break that only when necessary (like the cases you mention above).

1. Except for long / steep downhills, just start the coast at lower speed so as to not exceed the speed limit.
2. Again, start slow at the top, and use engine braking to control speed. Try to fit some neutral in between the curves if possible.
3. Again, start slow. If it's a STOP, DFCO. If it's a light, DFCO just enough to hit it on green.
4. If you don't have DFCO, why are we even talking about this? Neutral!

So I just went through this entire thread and this made the most sense to me. On the freeway, Pulse and Glide works best, down hills it's best to stay in gear if the hill is steep enough to maintain speed, if hill is not steep enough to maintain speed while in gear go to neutral. Now in town, is it safe to assume that coasting in gear while coming to a stop will be your best bet?
- Aaron

[UFO]

I drive mostly in town, with an automatic. If the light I approach I expect to turn green before I get to it, I will coast. If not, and my momentum will carry me through it, I engine-brake enough to maintain some momentum when it does. Of course I miss the light timing very often, so in general I will engine-brake to most lights, and use my brakes to stop if I need to. Then I put the transmission in neutral, as my fuel usage in D is double what it is in N.

Momentum is king. With my crude attempts at keeping momentum through more coasting and knowledge of DFCO, I increased my fuel mileage from 36-37mpg to a consistent 45mpg.

[SmellyCat]

That is a lot of words. After reading I'm in need of a summary.

1. Coasting in gear engine on, uses more gas than coasting in neutral engine on. Is that right? Sc

2.coastin in neutral engine off is the best.


My two ton Volvo SW will haul booty in N. down a hill for a long time. Down a hill in gear it is a slug. Auto trans seens to not mind it much if I give it some gas as I engage the tranny at 35-40.. Sc

[UltArc]

Originally Posted by ecomodded

Its like that car has it backwards?
It has a high rpm, well seems high to me, my car has a 850 rpm neutral idle and 1000 rpm at cruise.
Wow, big numbers you are getting, are the figures 80 to 60's with the scangauge or at the pump?

This is scanguage while driving. Coasting same speed, same conditions, in gear is 25% more efficient. I thought so, too, regarding the Hugh engine r p m s, but it is a small SUV.. I shift around 1200 r p m in my car, but that is an auto for you. She has been trying more techniques, and get early Christmas present was a SCii, so we will find out her mileage Monday

Originally Posted by SmellyCat

That is a lot of words. After reading I'm in need of a summary.

1. Coasting in gear engine on, uses more gas than coasting in neutral engine on. Is that right? Sc

2.coastin in neutral engine off is the best.


My two ton Volvo SW will haul booty in N. down a hill for a long time. Down a hill in gear it is a slug. Auto trans seens to not mind it much if I give it some gas as I engage the tranny at 35-40.. Sc

Every vehicle is different, is the point. My Mustang is more efficient in gear up to 25 ish. But that is because it will keep climbing by engine idle. Each car is different, with trans, and fuel cutoff. So the best way to know is instrumentation and testing.

[Xist]

Yes, transmissions made after 1995 are supposed to cut fuel when you release the accelerator, but you cannot really know until you buy me a ScanGauge.

Okay, buy yourself one. I am just being cheap!

[undata]

The few times I have driven an automatic, it seems like the thing is coasting when I take my foot off the gas. But whether or not, when you drive around with an automatic, you're hauling around the huge heavy transmission system. Unless you're sharing a car with person(s) incapable of learning to drive a manual, why not just get a manual transmission?