This seems to be a common argument in my group of friends. Some people seem to think that putting the car into neutral while going down a hill is better since the engine stays at a lower RPM and saves gas. Others seem to think that, since the car accelerates down the hill faster when it’s on neutral, you’re wearing out your brakes.
So what is the preferred method of driving down hills? I usually just keep the car on drive, and I assume most people drive that way as well.
Also, why does the car go down a hill faster on neutral?
The correct answer is: Neither. You should (on an automatic) put it into “2” or even “1” if it is on a steep hill. This will provide additional engine braking and save your brakes, and the engine control computer knows enough to be parsimonious with the gas. Similar for manual transmissions. Select a gear that allows you to descend without braking.
When going downhill in my car, the engine shuts off and the batteries are recharged.
In another car, the computer controls the engine such that the econometer reads 99 mpg.
In the classic car, with its manual transmission, I leave it in gear. Though in my nearly-identical first car I’d shut the engine off at the top of a winding mountain road and coast for several miles. Not smart, if anything untoward happened; but it saved me gas when I was a strapped-cashed teenager.
You should never go downhill on neutral. You’re going to get into trouble if this is a big hill. The brakes are going to overheat and they are going to fail. IIRC, there are multiple signs on the road down from Mt Washington reminding people to downshift and be careful with their brakes.
Bored as I often was, waiting to give someone a lift, I got a lot from my old Honda manual. The book recommended that for an autobox, you should go downhill in the same gear setting as you went uphill in (assuming that you’re coming back down the hill again I guess…).
In any case, from common sense and other threads on the subject, leaving your car in neutral is pretty much a no in any situation where the car is in motion.
Most of the answers so far depend on the steepness of the hill. You should be in a low enough gear that you do not need to use your brakes more than, say, 10% of the time. On a sufficiently gradual hill, this can be the case in Neutral.
The Spanish driving code specifically forbids “bajar a vela,” i.e., going downhill on neutral. I don’t know where did the legislators get their data, but the idea is that when you’re on neutral you have less control of the car than with a low gear in.
Your not saving gas by putting it in neutral. You are probably using more. Just because the engine will be turning faster to help slow the care does not mean it is sucking in more gas. Modern engines will be effectively shut off with no gas going to them. If you are in neutral, the engine will require gas to continue to run.
Just leave it in drive. Or pull it out of over drive and in extreme cases, put it in 3rd or 2nd (depending on how many speeds you have). I live in the rocky mountains and drive over the continental divide every day. Going to neutral is foolish, and dangerous.
eta: Sorry to be so blunt, but that’s just the way it is. Going to neutral is a bad idea.
I’ve heard that too and wondered why. Of course if we’re talking about a really steep hill, you run the risk of using your brakes too much and overheating them, potentially rendering them useless.
I can see that you’re “wasting” gas in a way…the engine is using gas to idle and if you’re coasting, none of that energy is going to the wheels.
If you really want to save gas and shut the car off, you lose power steering and power brakes, so there’s a safety issue. Plus if you’re not careful you’ll lock the steering wheel and that could REALLY dangerous because you’d have to restart the car to get control back while flying down a hill.
IIRC the law says you’re never supposed to stop or park on a railroad track. 99.999999999% of the time you could get the car back in gear and drive away safely but that tiny fraction isn’t worth risking because the results could be so dire. And hey, are we talking about a brand new car that runs like a top or some guy’s old beater work car? They may bias laws with the worst piece of crap on the road in mind…if the beater can’t be put back into gear after coasting, that may be pretty bad.
So my WAG is that the legislators may have realized that there are particular set of circumstances in which coasting may not be unsafe, but let’s not even go there. And some laws may just be on the books for the post mortem. They inspect the cars after a wreck, see that one was in neutral, and realize that that contributed to the accident. Having the law on the books provides a legal “We told you so.”
Because is it much easier to lose control of your car if things go wrong. Also, these laws were enacted back when cars were big and heavy and had crappy braking systems. One also runs the risk of blowing their transmission to pieces and in the case of automatic transmissions, you are putting excessive wear on the torque converter, the engine side is spinning much slower than the transmission side. On cars with power steering, the power steering pump is also running at idle speed often increasing steering effort. On cars with speed sensitive steering, the steering effort when the engine is idling is reduced which can cause problems if one as to make an emergency maneuver and the steering effort is less than anticipated. This can cause an over correction and the unforseen results that come with it. These types of laws are put in place to not protect us from others, but to protect ourselves from our own stupidity.
What do you intend to do when you get to the bottom of the hill? If you need to drive immediately up the other side of a valley, then putting the car in neutral enables gravity to accelerate the car, so you won’t need to expend as much fuel driving it up the hill at the other side.
Some of that effect depends on the gradient - on a fairly shallow one, the terminal velocity of the car might be quite low due to wind resistance and friction.
If you need to come to a stop at the bottom of the hill, it’s a different question.
In this post I question the term autobox. I assume that would be an automatic, then you continued with going downhill in the same gear as you would use to go uphill. That is the recommended procedure for a manual transmition.
As posted by “enipla” taking the selector out of overdrive is a good thing to do as there is very little engine braking while in overdrive.
Not to many drivers will downshift unless they are mountain drivers like “Enipa”.
I tried my best to correct a bad habit one of my old car-pool’er had of depressing the clutch pedal at the same time he applied the brakes on a downgrade where we had to turn at the bottom. He would even downshift the pickup at the top of the grade but not let out the clutch until the speed was reduced to the turn speed. He always believed that it was to hard on the clutch. I on the other hand downshifted every time and never had to touch the brakes, but old Dick was set in his ways and nobody could change him.
May he RIP!
I put my old automatic clunker into “2”. I was told eons ago to never never ride the brake down a big hill or they will burn out. Now I worry about the guy behind me’s brakes giving out!
I only drive manuals, so I’m not sure if I phrased it correctly. The booklet said to put the selector for the automatic in the same setting (the car had 1-3, 1-4, something like that) that you used to go uphill.
