I'm probably going to get blasted for this but here goes anyway. In my normal driving I go down a good amount of some pretty long hills. As long as traffic permits, I've always coasted down these hills with the engine off. My old car had a standard keyed ignition switch which I turned off and then immediately back on so I could immediately restart the engine by putting the car in gear and lightly releasing the clutch. Pressing the start button on the mini will not turn the engine off while you're moving, but pressing and holding the button down for a few seconds will shut down the engine. I then immediately briefly press the start button again to activate the ignition and electric steering pump. You only get a couple of pumps of the brake, so like I said this is only safe when traffic conditions permit. I also keep the car in high gear with my foot on the clutch, so I can have power almost immediately - no wear on the throw-out bearing because the engine isn't turning. My gas mileage has gone from 34 to 37 mpg since I started doing this. OK, blast away.2009 BRG Clubman 'S"

 

That's pretty dramatic. How much time/distance coasting are we talking about? The alternative is to coast in neutral with engine on, so it implies that idling in neutral is much higher gas consumption than I'd expect.

 

I actually clocked the downhill portions at 6 miles out of a 35 mile trip. I should mention that there are a few really long traffic lights where I also turn off the engine or at least dead coast to it, and then restart when it's about to turn green. I could probably do better on the MPG's if I got rid of those run flats which have very poor rolling resistance.

 

[quote=minilovr;2978964]I'm probably going to get blasted for this but here goes anyway.

 

In-gear coasting uses zero or near-zero fuel, so the only "waste" of energy relative to turning the engine off completely would be the slight "load" on the wheels to keep the engine spinning. All else being equal, the difference between engine-off coasting and in-gear coasting should be incredibly small (certainly not a 10% increase in round trip mileage), and being in gear with the engine on is much safer for everyone.

No offense, of course, but color me skeptical about the mileage increase, and however you slice it, I'll trade brakes and steering for an increase in mileage anyday. Put another way, if you drive 15,000 miles per year, you'll save a grand total of ~$100 per YEAR in gas going from 34mpg to 37mpg. I'll keep the steering and brakes.

 

If you would convert that puppy into an electric drive version, you could improve the mileage a bit more.

Jack Rickard
http://EVTV.me

 

It can go either way depending on which tires you choose. Actually the stiffness of runflats resists deformation which tends to decrease rolling resistance.

 

I thought I read somewhere that if the car is in gear but is "coasting" it actually knows to shut off fuel to the engine so it really isn't using any. I have kept the car in gear while rolling downhill and I know the "current MPG" readout will show 99.9 mpg while doing so. Having the car coast in neutral supposedly uses more gas since fuel is not "shut off." So count me in with the keeping the car running and in-gear crowd, having full control over steering and brakes at all times.

 

I'm with Blainestang on this. If you do not press the accelerator and leave the car running and in gear, you will use no fuel right down to idle. You will have pumping losses, so you may not be able to go quite as far without adding throttle. If you try to coast with the engine on, you will use fuel, but not very much (someone with a scangauge should be able to tell us GHP burned at idle).

 

By keeping it running, not only do you have brakes and steering, you also save on wear of the starter, and you won't be running your battery down.

Mark

 

As a deputy sheriff I can tell you it's against the law and and a safety issue. What if you need that power to get out of the way of someone/something or avoid something? Stop being so cheap! Some of your cars other safety gear won't work either.

 

A 10% increase in fuel economy for a 75% increased chance of a fiery death. Seems reasonable.

 

Hey... I was just checking out your videos yesterday. There's a thread someone made about them somewhere around here that you might want to post in there, too.


I was thinking the same thing... although the relatively high weight isn't great for mileage, and there are more variables, of course.


Yeah, when coasting in gear, the internals spin primarily or completely by the momentum of the car turning the wheels, so there is very little or no fuel being added.


I think it might even be illegal to coast by putting the car in neutral in some places, but don't quote me on that. Shutting the engine off while moving is definitely illegal, though, like you said.

 

Did you have a Toyota before?

 

Back when I was in high school (when Smokey and the Bandit was still playing in theatres) we used to call a variant of this "Mexican Overdrive".

 

ETA - My husband lobbied long and hard for me to buy a Prius, when my heart was set on a MINI.
Whose laughing now?
He just dodged a bullet too.
His Avalon missed the recall by one year.
I have to admit, I did have a Toyota Corolla for 16 years and it was a great car.
I had to finally get rid of it when the floor was open to the road and the doors flew open whenever I turned a corner.

I used to coast in neutral down one of the only hills around here. I loved that 99.9 mpg read out. Recently I noticed that I get the same read out when the car is in gear. It was such a surprise to me! Since that day, I keep the car in gear, get the same charge out of the 99.9 mpg read out, and know that I have better control of the car. What I had not heard was that cruising in neutral may actually waste gas.
Thanks for the information.

 

since coasting downhill in gear does not consume any gas, wouldn't this "technique" actually burn more gas due to the amount needed to re-fire? I'm calling shenanigans on your MPG savings.

as for the obvious safety concerns involved with killing power while motoring all I can say is it frightens me to be sharing the road with you.

seriously, this post is so silly, I am starting to doubt the reality of it entirely as i write my reply.

 

dumb, dangerous, and ineffective. consider yourself blasted.

 

Cliffnotes:

- The actual difference in fuel usage between coasting down the hill in gear and shutting the car off while rolling down the hill is negligible.

- Any mileage benefit observed is from shutting the car down while sitting at a stop light (or some other variable that changed), where it is much safer, but probably still illegal.

 

Can you share with NAM what the law is concerning this issue?

Is it illegal to coast out of gear? ...to turn off the ignition?

I've heard of this type of restriction cited before, but I'd be curious to know that the exact regulation is, and what law is being violated.

 

That is just taking "hypermiling" much too far.

What if a deer jumps out in front of you? Stop being so cheap, and unsafe. Put the car in neutral, if you feel obligated to appease your hypermiling agenda, but definitely leave your engine running. This is just silly, and of no benefit!

 

I didn't find anything for turning off the engine, but coasting in neutral is illegal in most states. Enter "vehicle code coasting prohibited" into Google, and it will return links for many states.

Even in Nevada which is not as strict as other states for some regulations.
http://leg.state.nv.us/nrs/NRS-484.html#NRS484Sec459

 

Thanks!

 

Just curious, how could you possibly convict someone of driving in neutral.. it would honestly be impossible to know if he was in gear or in neutral from the outside.

Also, coming from a previous Prius owner, this is the dumbest idea I've ever heard of. Then again, I'm one of the few Prius owners who only averaged about 44mpg because I actually drove like a normal human being.

 

Wow, talk about a safety hazard. That's all I will say.