1) Shifting into neutral from drive to avoid breaking, and back. IE. when rolling down hills, to save on gas and when approaching stop lights/signs.

2) Shifting into neutral, turning the engine off (again, to save gas) and just coasting.

Could these cause serious damage to the engine over the long run?

Auto transmission.

1) What? Normally you get a little engine braking in drive, but not in neutral, unless you're going real slow.

2) I'm not particularly knowledgeable on teh automatics, but I believe the transmissions oil pump is driven by the engine, so if the car is moving with the engine off, happy unlubricated gears for you, sir.

coasting with the engine off does however put you and those around you in danger....

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It'd be no different to avoiding someone driving slowly, and I'm assuming that he isn't doing it in anything like traffic. The brakes on his car will work regardless of whether or not the engine is running.

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It'd be no different to avoiding someone driving slowly, and I'm assuming that he isn't doing it in anything like traffic. The brakes on his car will work regardless of whether or not the engine is running.

I'm guessing he said that because of the point that Nereth brought up, about the transmission oil.

Depends on the transmission, I believe Mopar 727s and 704s run the trans fluid pump in neutral.

However, I wouldn't recommend shutting the engine off while in motion, due to the fact that you no longer have power steering, and will fuck yourself up trying to turn.

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It'd be no different to avoiding someone driving slowly, and I'm assuming that he isn't doing it in anything like traffic. The brakes on his car will work regardless of whether or not the engine is running.

Brakes won't help where you need to steer, or if you suddenly need to accelerate.

Technically, the brakes won't work with the engine off. The vacuum booster only has enough stored vacuum for a fairly small amount of braking, and the braking you get from pushing it without any vacuum assist is a fraction of what assisted braking is. So, if you shut the engine off and try to come to a stop from highway speeds, you will probably be in for a nasty surprise.

Brakes won't help where you need to steer, or if you suddenly need to accelerate.
You think that you can't steer a car if the engine isn't running?

You think that you can't steer a car if the engine isn't running?

Its a hell of alot harder.

You think that you can't steer a car if the engine isn't running?

Ever tried? Steering a power steering equipped car without the power part is pretty damn tough, a lot harder than just a manual steering box.

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It'd be no different to avoiding someone driving slowly, and I'm assuming that he isn't doing it in anything like traffic. The brakes on his car will work regardless of whether or not the engine is running.
The brake servo works off engine manifold vacuum, so if the engine isn't running, you only get one full application of the brakes before there's almost nothing there to stop you. Very dangerous if you need to do an emergency stop.

So-called hypermilers sometimes fit electric vacuum pumps to their cars to allow the engine to be switched off safely.

I guess this is what I get for being a bike kiddy. All of our things still work regardless of whether or not the engine is on. I haven't driven a car for a good few years now.

Seriously, why bother to turn the engine off? Coast in neutral if you must, but do you really feel the need to kill it for an added.... what, 1/10th...1/8th of a mpg?? Besides the dangers and fact that auto trannies can be damaged by this... it puts extra wear on the starter, if not more.

Nonsense, you can avoid the starter wear by just popping it back into drive. :D

if youre putting your car into neutral or just shutting it off for decel, youre not doing anything to help your gas mileage. When you lift off the throttle in a fuel injected car, fuel is cut to the engine.

On my way home from work I shut off my engine and coast down a three mile hill, then just pop start it just before I get to the bottom. My II has a manual tranny, and no power steering or power brakes.

Ah, right, the Mustang. You're golden in that case.

Depends on the current operating conditions.

Manuals at high speed that have the throttle cut will also generally cut the fuel, since the wheels will keep the engine turning so it wont stall.

Autos at low speeds, not so much.

It also depends on how intelligent the ECU is. Some won't bother with such fancy-pants stuff.

Save 3$ a month.. Wow, biggie.

Is 3$ worth being without control? Brakes, steering, controled acceleration...

But being as awesome as you are, you dont need any of them do ya?
Well you got the muscle for the steering wheel, and you can always use your hand-brake. So it seems pretty cool. Do it. No worries.

idk about you, but gas here is $1.40 a gallon now. I was doing donuts in a snow filled parking lot and probably wasted a gallon of gas in just a few minutes. I don't give a fuck about my mileage anymore with prices falling like they are.

Fuck you

I have snows and can't do donuts :o

Fuck you

I have snows and can't do donuts :o

I dont have snow yet and I can still do dounuts. :D

I dont have snow yet and I can still do dounuts. :D

I meant snow tires :D

I was doing doughnuts last winter with snow tires on. had no problem. Even when the snow melted.

Maybe he means he just put new tires on?

Aggressive TCS + Knobely tires + Heavy car =/= donuts

Yeah, it's got new snow tires on it. A nice fresh pair.

Although, it must be said, my dad had a 2001 XJ8. In the snow, dognuts, and damn, that was fun.

My apartment complex has a number of sharp turns between the entrance and my building. I throw the rear end out around every single one of them. :D

Rocko, what kind of car are you in these days?

Depends on the transmission

This. Some are turned by the engine, some are turned by the engine applying torque to the transmission, and some are driven by the wheels.

http://www.cardomain.com/ride/2508731

That one.

^ I like that. I went to see a Datsun Laurel, similar looking thing, I was really tempted but I don't have any money right now.

The computer has a program for coast - you will use more gas by shifting to N and coasting then leaving it in drive.

Sometimes...you will.

Remember that engine braking applies whilst it is in gear, so you will not be able to coast for as long.

If it's a long hill which requires you to brake anyway, leaving it in gear will indeed save fuel as the injectors will be shut off (in most cars, that is). However, if you want to coast for as long as possible, leaving it in neutral with the engine idling will probably save fuel as you will spend less time with the engine under power.

If you get what I mean...

Woah, haven't seen that name in a while.


I suppose it depends on the car, alot of older cars don't use power steering or brakes. But personally, I would not recommend switching the engine off while coasting or even putting it in neutral because it isn't worth the lack of active safety that being able to accelerate gives you, plus you would put alot of faith on your brakes considering the lack of engine braking. When I was down under and had the Falcon, I would usually knock it back a gear or two to regulate my speed.

http://www.cardomain.com/ride/2508731

That one.

That's really nice. I drive an 88 town car myself. Looks almost identical to a fifth avenue, just slightly bigger i think.

I have a friend who always turns his car off and coasts to a stop when his parking spot is in sight. I always thought it was kind of dumb and reckless.

Sometimes...you will.

Remember that engine braking applies whilst it is in gear, so you will not be able to coast for as long.

If it's a long hill which requires you to brake anyway, leaving it in gear will indeed save fuel as the injectors will be shut off (in most cars, that is). However, if you want to coast for as long as possible, leaving it in neutral with the engine idling will probably save fuel as you will spend less time with the engine under power.

If you get what I mean...

However during that long coast in N, the engine will be sucking fuel and in OD there should not be much engine braking.

Keeping the engine turning at 'x' revs is pretty much gonna take pretty similar energy regardless of if comes from the fuel or the cars kinetic energy*.

Options:

- If you have kinetic/gravitational energy you don't want, eg that from going up down a hill or wanting to slow down for a light, you may as well put the ol' girl in gear and let that handle turning over the engine, rather than having the fuel do it while you apply the brakes.

- If you don't want to waste any of the cars kinetic energy (i.e. you don't want to slow the car down), you have no choice but to add some petrol instead. Whether by leaving it in gear and giving it a little gas, or having it in neutral and letting the ECU give it gas. Which is better? Hmm, I guess it would 'depend'. But I doubt its a big enough difference to worry about. Leave it in gear because that's easier and you have more control. That would be my choice. That may bump the revs up beyond idle, taking more energy than necessary... so use a high gear, and your better judgment.

*Well actually, using fuel instead of the cars kinetic energy will probably be less efficient because the ICE itself is crap at converting the fuel into useful work, the transmission being much more efficient at converting the kinetic energy into that same work. However, because if you use up kinetic energy, you will later be replacing it with kinetic energy from the same ICE, it should cancel out (taking a lot of assumptions here though).