Coasting for better mileage?

I have a 2009 4 cyl. 2WD man. stock Taco. I drive at 1900-2000 rpm between 60 to 65 mph. If I'm on a downhill stretch and slip it out of gear and coast, the idle goes down to 750 rpm. If I can do this on the highway for say 35 % of the distance, how much fuel would I save?

It's illegal to coast out of gear, I realize, but I'm curious to know how much difference this might make to my mileage?

Thanks to all the number nerds who might be interested in figuring this out, or already know how to do that.....

 

I'm no expert but I think if you let your truck in gear while going downhill the injector are not spraying any fuel ... If you put the truck in neutral the injector spray fuel to keep the engine running idle. I've read somewhere you actually waste gas coasting.

 

I don't coast in neutral because you never know when you'll need to accelerate out of danger instead of breaking.

 

Depends on the situation. If it's the kind of hill where you can keep but not gain speed in neutral, you'll save a little bit. Maybe 30% drop in instant gph but that can easily be washed out by the rest of the tank. On my truck the fuel cut doesn't kick in above 2000 rpm most of the time (that's about 54 mph on my 4WD) so it doesn't have that going for it.

About the only thing the four cylinder can outrun in 5th gear is a shopping cart so chances are you'll have to shift in an emergency anyways. It does take longer to rev match a lower gear from idle rather than ~2000 rpm though.

That said, I haven't done hardly any coasting since I had the six speed. No real need. The downhill fuel rate of the 2.7 in gear tends to be about the same or less as the 4.0L out of gear, thanks to that engine's high 1400 rpm at-speed idle. On that truck I'd see about a half mpg gain but I have a lot of flat land to traverse.

 

hahaha

 

I coast on long downhills, but never out of gear. Because at idle, the engine is still consuming gasoline. But above idle at about 1,000 rpm, Deceleration Fuel Cut Off (DFCO)kicks in and shuts off the injectors. So coasting out of gear with an idling engine consumes more gas than coasting in high gear with DFCO which uses no gas at all.

 

So what's the point of having neutral then? It's safe to assume and I'll admit I'm not an engine expert, that Toyota thought of this and the injectors are going to pump almost just as much fuel in Neutral that it does in Park to keep the truck running properly.. once warmed up of course. Anyone?

 

This is correct. You will use less gas by leaving it in gear going down hills. You can see this clearly with a A/F gauge.

 

To start your truck without running into anything.

 

I do it. I can't say how much it helps, though. Hypermiling FTW!

 

Oh canada... u cant coast in nuetral legally? Thats crazy

 

I do it all the time with amazing (many say unbelievable) results.

I've never once found a situation where accelerating while I was in neutral was the best option. Doesn't take much skill, since as already said I'd have to get out of 5th anyway.

Generally engine braking that cuts fuel also slows me down way to fast and the engine ends up running with more fuel overall then coasting.

I see the intersection 1/4 mile ahead just turned red and slip into neutral and coast all the way there, and maybe the light has gone green by the time I get there. In gear I wouldn't be able to get off the gas til I'm almost there or come to a stop half way there.

If you're on an extended downhill where you would have to brake anyway, it is always better to stay in gear and use no fuel.

 

If you want to hypermile get a Prius.

 

those hypermilers can be annoying at times

 

so what were all saying is.....is that we all do it? and if we don't..we'd like to.

 

Every vehicle can be hypermiled, that's what this thread is about. 37 mpg summer tanks out of my Tacoma shows a Tacoma is perfect for hypermiling.

I'm a hypermiler and curious how you guys identify people hypermiling.

Is driving the speed limit being an annoying hypermiler?

How are you being annoyed?

 

http://www.tacomaworld.com/forum/4-cylinder/183149-anyone-tried-save-gas.html

 

I try to coast to stop lights using this method.

I don't know how you get such great mpg numbers. You should start a hyper miler's guide thread if you haven't yet.

When you accelerate from a stop (ie at a signal) do you accelerate noticeably slower than the traffic next to you? The only way I could see myself getting anywhere close to averaging ~20mpg would involve holding up everyone behind me while I inch along between 1000-2000rpm.

 

I accelerate at 1/2-3/4 throttle but shift at 2000 rpm. No slower than most.

 

Pretty sure he has a 4 banger nd if u have a v6 that could be his bigget advantage. Ive often wondered how much it actually saves slowly accelerating. I have the torque app and it shows instant mpg, and while i do get better instant mpg slowly accelerating, it means im in a lower gear for a longer period of time. I.e. 1st i get 2-5 mpg 2nd 4-7 3rd 6-11 4th 9-15 5th 13-25 ( numbers are made up but pretty close from what i remember) this is while accelerating or maintaining speed on flat ground. If i have to drive half a mile before i get to overdrive getting at best 15mpg meaning in that half mile i burned a 1\10th of a gal or so getting up to this point, will i not use less fuel to drive reasonably (1100-1800 rpms) to get to overdrive in say half that distance?