Side effects of slipping the car into neutral while driving?

D

Dunhausen

Joined
Apr 29, 2006
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My city's wedged inbetween a mountain range and a valley, so all the east-west roads have a westward slope to them, the advantage being that it is always possible to traverse the city westward with your engine turned off (starting it up again at red lights and such).

I was wondering, though, if there might be any adverse effects to this method of gas conservation?
 
That depends on the vehicle. Most automatic transmissions are not designed to be rolled in neutral for long distances or at speeds in excess of 45 mph. The transmission is lubricated by a pump driven off the input shaft, so if you shut off the engine, the lube goes away and you can burn up the tranny. Some manual transmissions are not designed for being towed either, so check your owner's manual.
 
1) It might be illegal to drive in neutral--best to check local laws.

2) If you drive stick, you can use a lower gear to help slow the car during a long coast downhill. With the engine turned off, you're only using the brakes.

3) Other than that, it would not be a good thing to have to start the engine quickly should an emergency situation develop. "Muscle memory" will most likely have you steer, brake or accelerate to avoid the threat. Whether your muscle memory will "remember" to have you start the engine is another matter.
 
Two thoughts - the inlet manifold and hence your brake servo will run out of vacuum with the engine off, so your footbrake will get heavier to operate. May be a problem if you need a sudden stop.

Many modern engines use no fuel if you are coasting downhill with your foot off the throttle. Slipping into neutral and letting the engine idle will use more.
 
Switching the engine off??? That could be dangerous: re-starts can cause the exhaust to blow due to accumulated unburned gasses, no power steering on or ABS servo??:eek:

Because most of our cars in Europe are still manual(shifting is FUN!) you can glide down slopes OK in neutral with the engine ON and save fuel (look at the car's fuel computer, nice economy) But you still have less braking power from the engine, good feeling though shoving it back into 5th or 6th as the slope ends:D
 
My city's wedged inbetween a mountain range and a valley, so all the east-west roads have a westward slope to them, the advantage being that it is always possible to traverse the city westward with your engine turned off (starting it up again at red lights and such).
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Actually shutting the car off like that is just not a good thing to do. Starting up the engine frequently puts more wear on the engine and ignition system and will probably eat up more gas than coasting with the engine on (depending on how long the car is off for). Add to that that it's illegal, and dangerous because you're losing power brakes, steering, ABS, TCS and whatever other systems your car might have.

If you drive an automatic (which I'm assuming you do) just force it to upshift by taking your foot off the accelerator when your engine speed is high enough- it won't take long to figure out your car's approximate shift points. If you drive a manual, just coast in your highest gear, which will use less gas than coasting in neutral because fuel isn't injected anymore when you're in gear with no throttle. As long as you're at the really low end of your highest gear, you shouldn't notice too much compression braking so you shouldn't have to give it gas much.
 
Also if you shut off your engine, to the off position you might run the chance of locking the wheel. Very bad. coast with the engine on you are not going to burn to much gas. if you tow a rear drive vehicle I also recomend to remove drive shaft so you do not damage trans. Just remember to use trans plug to keep the fluid in.
 
I see no downside if you have a manual transmission, although I wonder what the net effect on mileage would be. You'll be using your brakes harder if you have to slow down, though.

On an automatic, well, just be careful. I almost ruined my grandmother's transmission when I was 16 and tried to do just that and went right past neutral and into reverse :eek:

There must have been some sensor that stopped it from trashing the car because it didn't lock up the wheels and immediately start spitting metal parts all over the place, but it couldn't have been good.
 
If I may add two cents from the perspective of living in a wintery climate, and this is a bit off topic, but slapping your car into neutral is recommended when losing traction or skidding in particularly treacherous driving conditions. The manouvre won't save you gas--you only put it in neutral for a few seconds--but it will possibly save you from ditching and/or rear-ending another car. If you're interested in learning the trick just google it online. It is an essential winter-driving survival tip that even many Canadians don't know about (or try).
 
Actually turning the car off, you'll have no power brakes!! And no Power Steering!!

And stopping and starting again at each stoplight will use more gas than having the engine idling the whole time.

Is this post for real???

-Bob
 
The new hybrid vehicles take advantage of the terrain you are stating in your post. When the vehicle rolls down hill no gas it used and the engine automatically turns off and the electric motor takes over.

When the driver uses the brakes, the electric motor becomes a generator using the kinetic energy of the vehicle to turn that energy into electricity stored in the batteries, unlike conventional vehicle brakes that simply turn that energy into wasted heat.

I would look into these vehicles if you are interested in this kind of technology. It looks promising, and with gas going up, pretty soon this will be the standard in the automotive industry in a few years.
 
You could get an old SAAB. My SAAB 96 from the 60s had a freewheeling feature.

You reached under the dash, pulled a lever and the engine was disengaged from the transmission. No drag and better economy.

The downside was that the lever was stuck way under the dash so it was real hard to reach. Also living on the Gulf Coast, I didn't have much use to use the feature.

Also on the old SAABs, the rear seat folded down and you could make a bed by sticking your feet in the trunk. They even had a bed kit option you could buy from the dealer.

Chad
 
You could get an old SAAB. My SAAB 96 from the 60s had a freewheeling feature.
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Now there's some good advice! :D I read once that the freewheeling feature helped SAAB win a lot of the rallies that they otherwise would have lost by having less powerful engines than the competition.
 
NeedleRemorse said:
I read once that the freewheeling feature helped SAAB win a lot of the rallies that they otherwise would have lost by having less powerful engines than the competition.
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That and their ability to slide across the finish line on their roofs. :)

Chad
 
the most important side effect i can think of is driving off a cliff or into the side of a mountain or into another vehicle because you couldnt steer, accelerate, or brake properly.

bad idea.
 
The transmission also slows down the car while coasting downhill -- if your foot isn't on the accellerator you will not burn much gas. Whaddaya think yer gonna save each week? Five bucks? For coasting in a dead car with stiff steering and no brakes? You don't have five bucks?

Shifting a running vehicle into neutral to coast is potentially dangerous, but actually turning the ignition off might even constitute reckless endangerment. Do you want a Darwin Award?
 
ChadHahn said:
That and their ability to slide across the finish line on their roofs.
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Mrsaab.jpg


Erik "On the Roof" Carlsson

:D
 
ChadHahn said:
You could get an old SAAB. My SAAB 96 from the 60s had a freewheeling feature.

You reached under the dash, pulled a lever and the engine was disengaged from the transmission. No drag and better economy.

The downside was that the lever was stuck way under the dash so it was real hard to reach. Also living on the Gulf Coast, I didn't have much use to use the feature.

Also on the old SAABs, the rear seat folded down and you could make a bed by sticking your feet in the trunk. They even had a bed kit option you could buy from the dealer.

Chad
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Those were nice quirky REAL Saabs in the days before big bad GM swallowed them up and left them to stagnate....
 
willgoy said:
Those were nice quirky REAL Saabs in the days before big bad GM swallowed them up and left them to stagnate....
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Why is it that these car companies buy other companies that have a good reputation and then precede to p*ss all over it?

They buy SAAB and then just rebadge Opels. They are even doing it with Saturn.

I read that in the 80s GM was losing a million dollars a day. I don't know if they are still losing that much money but I guess with a company as big as GM it will take a lot of years of poor management to totally run them into the ground.

On a happier note: I also read that Erik Carlsson didn't like the rear wheel camber on his SAABs so he would load the rear seat up with neighborhood kids and drive over rail road tracks until the wheels were angled the way he liked them.

No fancy computer aided design needed for him :)

Chad
 
Its funny that you ask this question, My local news did a big story on this. It is called driving green, they featured a guy that kills his engine while going down hills and even while slowing down to make turns. they rode along with him and it was scary to say the least. He claims that his Ford explorer gets 60mpg in the city driving this way.
-Eric
 
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