Going down hill


#1

A little over two years ago my family moved up to a mile high mountain town. Driving in the mountains on a regular basis is a new thing for all of us, and it began an arguement. My mother insists that those of us with manual transmission cars are destroying our cars by going down hill in neutral. Those of us who drive manual transmissions find driving down hill in neutral pleasant, gas saving, and fun. None of use have found anything wrong with our cars, at least nothing we can trace to driving downhill. So who is right? Will driving down hill in neutral ruin the car, or is there really not a problem? Please advise.


#2

It will not ruin your car. It will not cause even a tiny bit of damage. Nor will you save any measurable amount of gas, however.

Even so, mama is right although not for the reason she gave. Always keep your car in gear on those downhill stretches. The idea is a matter of speed control, and saving wear on the brakes. You will also prevent any attack of brake fade, which can be deadly, although does not appear to be an issue here.

Finally, I should point out that in many states your action is illegal. Also unenforceable, but I thought you ought to know anyway.


#3

I agree with SteveF except for one point. Your practice of driving downhill in neutral WILL damage your car and perhaps your physical being, if and when you lose control of the car due to not having it in gear. The reason why this practice is illegal is because it is easy for the car to gain too much momentum by keeping it in neutral on those downhill stretches.

And, as Steve pointed out, when you do use your brake, you will be applying it much harder and for a longer period of time than if you kept the car in gear, thus possibly resulting in brake fade. In case you are not aware of what brake fade is, that is a situation where you lose most of the braking system’s effectiveness, due to overheating of the brake pads. And, the cause of brake fade is frequently…exactly what you are doing.

If you want to be safe, I suggest that you downshift at least one gear when descending long, steep hills. The tiny extra amount of gas that you might use is a small price to pay for being able to keep the vehicle under control.


#4

I agree with SteveF and VDCdriver that coasting in neutral, even for long distances, will not do any harm. However, I part company with them on the safety aspect. I do it frequently, but I know at the top of the hill that the car will not reach an unsafe speed before reaching the bottom. If you need brakes to control your speed, it’s better to leave the car in gear to save the brakes. Use a high enough gear that you approach the highest safe speed without exceeding it.


#5

Another reason not to coast down hill…Should the engine stall for any reason while coasting, you suddenly will find both the steering and brakes take MUCH greater effort to operate. Things can get out of hand while you are dealing with that problem…


#6

OK Time for my opinion.

It will not damage the transmission or any part of the car, assuming it does not cause an accident. In fact it can very slightly reduce wear on some parts.

The real question is do you need to use brakes when doing this. If so there is a very real potential danger. The brakes can overheat and then fail. Note: Make sure you replace the brake fluid every two years, the moisture it can build up will greatly increase the chance of this safety issue.

Other safety issues, while real, are very remote and I would guess would be outweighed by other factors.

Yes it will save gas, if you have a gasoline car, but not really much and then only if you turn off the engine and the does offer some serious safety questions. If you have a modern diesel, it will save more fuel to keep it in gear, as most modern diesels totally cut off all fuel to the engine under those conditions.

In the end the differences (with the exception of safety issues of having the engine turned off or over relying on the brakes to slow the car) are really far too small to worry about.


#7

You’re not damaging your cars, but you are endangering yourselves. Coasting downhill in neutral is dangerous, not “fun.”

It doesn’t save any gas, because as long as your foot is not pressing the gas pedal, the fuel injection system delivers only enough fuel to maintain idle, regardless of engine speed.

Leave it in gear. The engine braking will prevent you from building up too much speed, and it will save wear on your brakes.


#8

Thank you everyone for the advice. My Mom loved your answers. Lol


#9

Agreed that it will not hurt the vehicle one bit.
While this practice could be unsafe, I think it all depends on how the person behind the wheel handles this.

I’ve done it, with both car and motorcycle, while traveling in hilly or mountainous regions but have always made sure that neither the vehicle or myself has gotten carried away with the process.

When the speed becomes a bit excessive I simply drop the transmission into gear, allow it to slow, and kick it back into neutral again.
If the area in question is Colorado the one thing I would definitely keep an eye on are the signs denoting curves and recommended speeds ahead of you.
Two miles of 7% grade and running up on a 45 MPH curve can be a real eye opener. :slight_smile:


#10

Two miles of 7% grade and running up on a 45 MPH curve can be a real eye opener.

oliveygal, if you ever decide to run down Tioga Pass in the Sierras when visiting Yosemite Nat’l Park, DON’T try it in neutral unless you are looking to take the expedited vertical route down as a last hurrah! Tioga is something like five miles of 7% to 9% grade with some rather interesting curves and no barriers.


#11

Many newer gasoline cars also shut off all fuel while going down hill in gear, so the OP could be using more gas by being in neutral.


#12

As the others have said, don’t do it. It’s dangerous, probably illegal, and won’t save any significant amount of fuel.


#13

As others have pointed out, you will save virtually next to nothing in gas, wear out your brakes prematurely, or have them fail altogether, and needlessly endanger yourself if the engine stalls.

Truckers always use engine braking to save their brakes. They should be interested in fuel savings, if anybody is.

We had a very elaborate post on this a few months ago. Your mother is right and where I live (in the mountains), no one I know of indulges in a REALLY DUMD HABIT like this!!


#14

I have lived in the Rockies of Colorado near a town called Bailey for over 29 years. My driveway is at 8,868 ft. above sea level. Almost anywhere I go is downhill—except when I’m returning home, of course. In Colorado, it is illegal to operate a motor vehicle, ANY motor vehicle, on a public road that is not engaged in a gear (except for towing, etc.). I once popped my '71 Chevy Van into neutral going down Turkey Creek Canyon from the Aspen Park area heading (sorta) North to Lakewood. I will never, ever try that again! I couldn’t get the vehicle into third gear (3-speed manual ‘on the column’) fast enough.

The small amount of potential/possible fuel savings is not worth the potential/possible safety issues that you will run into. What are you going to tell the Trooper who investigates your accident, if you survive? He/she will determine the most probable cause of the accident. What if a deer, elk or bighorn sheep comes flying out onto the road from a road shoulder? How will you control the vehicle if it’s in neutral? Now, as you’ve explained to the Trooper, you were attempting to avoid a road hazard of some kind (how about that bale of hay falling off a truck or any kind of open truck spilling a load or partial load, especially on a curve?) while you were “coasting” out of gear. Trooper: “Here’s your ticket!”. Now see what your insurance company says about your illegal operation of a motor vehicle resulting in an accident. The Ins. Co. will be looking at any possible reason(s) to reduce or deny your claim. Oh, by the way, “Here’s your sign”. Just my 2 cents worth. (Colorado is now a ‘no-fault’ State).


#15

My opinion is still that it is only dangerous depending on the operator of the vehicle. If the operator is actually paying attention to the roadway and what lies ahead instead of text messaging friends and concentrating on their Starbucks latte there should not be a problem.

Every time I’ve been coasting the mountain grades in Colorado (been there a few dozen times) and exceeding the speed limit a bit I’ve been darned near blown into the weeds by the people who are going down the same road while IN gear.
Even on the 2-lane back roads I’m amazed at how many people there will blow past me at 60-70 MPH in a marked 40-50 MPH area with numerous curves.

Wonder if CO maintains a stat list about the number of vehicles rolling off curves? Many years ago, 4 guys from my town (knew 2 of them a little) got killed in CO when the speed they were going was excessive and the vehicle rolled off into a 300 foot ravine. Killed all of them.


#16

Everybody is correct in stating downhill neutral is dangerous, you need engine braking. Also, while not going steep downhill, soemtimes you need to accelerate to get out of trouble and if in neutral that will not happen.


#17

The difference is, if you’re hauling down the road in gear and find out you’re in to a curve a little too hot, you can still feed in more throttle and hopefully save it without heading off the road. Coasting around corners at high speed is asking for it.


#18

May we expand the subject to coasting. It is illegal, at least here in PA. Just ask my 16 yr. old who failed his driver’s test by pushing in the clutch too soon approaching a stop sign (almost level, slight down hill). Never heard of anyone being cited, even a trucker. I drive a Volkswagen Jetta TDI (diesel). Supposedly, the engine uses no fuel when it is being pushed. Therefore, I’m being more fuel efficient leaving it in gear going downhill. Although, a diesel is a high compression engine this car has no “compression” as us old time gas engine drivers understand the term-it runs away downhill so there is no point in using neutral; down shifting will red line the engine. Now you know why the truckers use those engine retarders (jake brakes). My son & I had never realized how much we use neutral or clutch disengaged until he was ripped apart by the license examiner. We coast up to a lot of traffic lights, usually popping the shifter into neutral when the tachometer hits idle in high gear. Why go through the wear & tear on the tranny down shifting when coming to a gentle stop in traffic? Here’s what I suggest to others: putting a car into neutral going down hill is fun & is possibly illegal. Don’t do it unless you understand “this is risky behavior” and could adversely affect you, your loved ones & those you don’t know at the bottom of the hill. If you must & you’re dealing with a short hill just disengage the clutch; this way if the engine stalls or something else peculiar happens you can bump start the engine. Don’t do this on long hills; your left leg gets tired & it wears out the clutch throw-out bearing. Let’s drive to save fuel & gasoline. A carburetor engine will use more gas being pushed but so minutely coasting is not justified. A fuel injected engine will not use any more fuel being pushed & may use much less (none). The results are coasting will not hurt the vehicle, may use more fuel & it does open up other risks.


#19

I did this in the Blue Ridge Mountains… and I ruined my rotors. The reason, the power assist to the brakes. If the engine is not engaged and revving as much as it would in gear, the power available to the brakes is less and their ability to grab the rotor is much weaker. This causes any small perturbation in symmetry to grow and cause larger more permanent damage.

You will probably save gas, but if your bottom line is cost, then don’t do this for the repairs that will probably occur.


#20

But you could jump start it. That would be a thrill at high speeds.