Hyper-miler question

I have gotten into a habit of putting my automatic tranny in neutral and coasting toward a potential stop. If the light changes, I push in back into drive gear.

Is this a good or bad habit?

Bad habit. It’s extra wear on your transmission and it isn’t going to save you any gas. Just take your foot off the gas when approaching a stop.

I wouldnt do it. if i forgot to put it back in gear, and a log truck were bearing down on me, I’d wanna be able to scoot out of there.

Definitely a bad idea.
In your attempt to save gas, you are actually putting a lot more wear and tear on the transmission’s clutches every time that you force them to engage.

Even if this saved you a miniscule amount of gas, the potential cost of overhauling your transmission (~$3,000, most likely) would greatly outweigh the potential gas savings. But, since it actually does not save any gas, you are essentially tossing a couple of dollars out the window every time that you engage in this behavior.

Can you explain why you are doing this?

It is to save fuel? Unless it’s an old car, as Xebadaih noted it’s likely causing you to use more fuel.

This doesn’t save any fuel and it’s a very bad habit. When you’re coasting in gear the engine is only getting enough fuel to maintain idle, regardless of the speed of the car, so shifting to neutral makes no difference is fuel use.

if your truck is just a few years old the fuel injectors are shut off while coasting in gear, which means the engine is getting ZERO gas. In this case shifting to neutral would actually burn more fuel than coasting in gear.

Bad idea. Anything that adversely affects your ability to immediately control your car in an unexpected event is a bad idea. This does so.

When I was teaching my kids to drive I always pointed out to them every time I saw an unexpected event that might have become an accident had we not driven with the assumption that the unexpected would happen. We never left the house without seeing at least a few. If you see one every drive, two drives a day, for one year, that equals 730 opportunities for an accident. Drive for 20 years and that’s 14,600 opportunities. Why tempt fate?

And then, of course, there’s the added wear to the shift linkage.

A much better idea is to simply plan well ahead for all stops and starts and do both as if you had an egg pearched on the edge of your passenger seat.

It probably uses more gas, it’s unsafe, it’s probably illegal, and your owner’s manual probably tells you not to do it.

There are no advantages to this, just disadvantages.

With an automatic, the car coasts when you take your foot off the accelerator. You don’t have to put it into neutral. Watch the tachometer. Therefore, no advantage.

Constantly shifting increases wear. If you need immediate power in an emergency, you won’t have it until you shift back into gear. Definite disadvantage.

It’s different with a manual transmission. When you take your foot off the accelerator, there is significant drag even in top gear. I don’t know if eliminating the drag saves enough gas to outweigh the disadvantages.

Don’t you think that if this were a good idea, engineers would incorporated this feature into the transmission itself. Like the free wheeling in an old 2 stroke SAAB, it allowed for continued better lubrication from the oil gas mixture. Can’t think of another valid reason for normal driving. BTW, depending upon what gear you are in, you still get some drive train braking…a good thing.

If you’re really worried about fuel mileage, a TRUCK is not for you.

bad habit

it is dangerous

The only situation where I might shift into N approaching a stop would be in snowy/icy conditions, when my speed drops below 5MPH or so, just so that I don’t have to overcome the forward force of the AT in gear. Especially on a downhill, sometimes you just can’t stop the car properly without.

The jury has spoken …its a bad idea. It did feel good to quietly coast to a near stop, with the RPM’s dropping by about 300. But, I can still coast in gear. I did not get any noticable mpg improvment …steady at 24.

Thanks for the thoughtful replies (except for one).

Compare RPMs for yourself if your car has a tach.
The results on my 06 Escape hybrid ; idle in gear -vs- idle in neutral… zero difference.
The results on my 92 Explorer ; Idle in neutral 900 rpm ; idle in gear when stopped 600 rpm.
I’ll leave mine in gear thanks.

That’s a good point. Why would a hyper-miler be driving a truck in the first place? It’s a little like someone who is trying to lose weight saying “instead of eating less, what would happen if I ate standing up instead of sitting down?”