Do you turn off your car at stop lights?

[Mdcastle]

I always drive very used vehicles- I bought my last one at 110,000 miles and the one before it at 140,000. I’d be worried about the starter going out when it’s time to start the car and I’m sitting in the middle lane on a 45mph road.

BTW, the longest red light in Minnesota is 8 minutes long, but that’s a specific situation and is unusual.

[GreasyJack]

Yeah, carburated engines were very inefficient in cold starts, but warm restarts shouldn’t have been any problem, fuel use wise. Turning your engine off at lights on a hot day was a great way to vapor lock the fuel lines on one, though.

[california_jobcase]

The “it takes more gas to start it than to shut it off” thing never applied to an engine in good repair even back in the day. Starting an engine only requires a richer mixture when it’s cold, and if you had to pump the gas pedal or hand choke a warmed-up engine to get it to start, there was something wrong.

Could have been a hassle with hand-cranked engines, though-

[Fubaya]

I like modern cars that shut down automatically, but I don’t like the idea of manually shutting the car down in traffic. I like to maintain control even when stopped. But I also wonder if cars break down more while driving them or while starting them? There’s a lot of dead cars on the side of the road, but many of those are tire/drivetrain issues or just out of gas and not sudden engine problems. Surely a significant percentage of break downs happen at startup. If 80% of your startups are done at red lights, you’re statistically going to be the jerk holding up traffic more often.

Batteries can go bad without warning. My last three batteries haven’t gotten weak and eventually died like you’d expect. They all started fine and I drove to the store or work then they wouldn’t start back. A couple times I had only turned the vehicle off for about 60 seconds and there was zero juice when I tried to restart it.

I’m not arguing against it, it’s generally a good thing. And if you do it and burn less gas, maybe my gas prices will be a little less. I just personally don’t trust vehicles enough and socially I’m worried enough about being the dummy whos car keeps dying in rush hour traffic that I wouldn’t do it.

[Ulfreida]

I turn off my engine habitually whenever I may be stopped for more than 30 seconds. I also engage in a number of other hypermiling techniques which boil down to the effort to evade either stopping or accelerating whenever possible. It isn’t any one particular thing, it is the constant practice of all of them which pays off.

[Kevbo]

The next suburb over from where I grew up had very poor/no zoning. (Commerce City, CO) The main road through it was multi-lane, limited access, but also had two lane frontage roads on each side. So you would have these signal controlled intersections with 4 roads, 6 total directions, and protected left turn lane/arrows for all but the frontage roads. Good gravy, if you caught one of those suckers on a fresh red, you could shut down the engine, read war and piece, and still have plenty of time to re-start your engine…and hope it didn’t cool down so much the defroster stopped working. In high school I worked at one of the only Pharmacies that delivered, so I got to drive through that hell hole a lot.

With modern fuel injection, it is probably about a wash on a normal light if you catch a fresh red. I will drop a slush box into neutral to keep the transmission a little cooler and let the AC load the engine, and of course always in neutral with a manual.

What I don’t get is people who leave the engine running in obvious “we ain’t moving anytime soon” situations: Construction zones with pilot cars, A Truck just rolled over in front of you and the whole road is going to be blocked until a wrecker comes and moves it, etc.

[Pai325]

I don’t do it at traffic lights, although the ones by my daughter are on about a two-minute cycle if you’re on a cross street, but I do it when I’m waiting for a freight to go by.

[steviep24]

I don’t but I know someone who does. I find it annoying actually. I’ll stop the engine if I’m waiting for a slow train though.

[Yorikke]

What? No, that’s ridiculous, and certainly worse for the car, the mileage, and the environment.

Joe

[Quartz]

I just put the hand brake on and put the car in neutral.

[Throatwarbler_Mangrove]

@ZenBeam

They said the same thing about florescent lights. I’d have to see a reliable cite to believe that.

The issue about oil wouldn’t apply when stopping the engine for a stop light. The oil wouldn’t drain away that quickly. I’m not sure why the water pump would be an issue either. It’s doing the same thing it does when stopping any other time.

When I lived in California, there was a long light on my commute home, and I would stop the engine for that one. I don’t have any lights near me where I stop my engine, but I did recently cut my engine for a train. Restarting it seemed almost effortless, because it was warmed up. I’d have a hard time believing it was somehow equivalent to three minutes of idling.

The thing about engine oil is not so much about the pumping but the operating temperature. Cold oil is more viscous than oil at a normal operating temp and won’t flow as easily around the engine, which is why cold starts are bad. If the oil is already at operating temperature shutting the engine off briefly won’t be too much of an issue.

A bigger problem IMO is the oil pumping in the automatic transmission. The transmission is operated by oil pressure generated by an oil pump driven by the engine. In addition to lubrication, the engine would have to start and drive the oil pump before the trans can shift into gear. If you’re shutting your car off at intersections then when the light changes you’re probably going to have to do all of this in a hurry.

Is this going to break your transmission? Dunno. However it is worth noting that the automatic start/stop functions that European market cars have were in the beginning only available on manual transmission and dual clutch gear box vehicles. The automatic transmissions at the time were deemed to be unsuitable. Supposedly this is more because the process to automatically start then engine, oil the transmission and shift into gear on an old automatic would take too long, but I can’t help but wonder if the durability of those parts might also have been a problem.

The very newest automatic transmissions, like the ZF 8 speed automatic, are designed specifically with start/stop in mind and have things like automatic oil accumulators that store and release pressurized oil without engine power. Maybe ye old 4 speed will be fine without it but I wouldn’t be too keen on finding out personally.

[Hairy_Bob]

@davidm

If I’m stopped facing uphill on a slope, when I release the brake, the engine starts quickly, but not quite quickly enough to prevent me from rolling back a slight distance. If someone is stopped too close behind me, I could roll into them.

The answer in this situation is to let up on the brakes just enough so that the engine starts then quickly reapply them till it’s up to speed and I can safely move my foot to the accelerator.

Imagine this scenario if it didn’t start until you pressed the gas pedal. You’d be rolling backwards the entire time your foot was moving from the brakes to the gas.

Were you not taught to apply the handbrake every time you come to a complete stop? If you are rolling backwards whilst in forward gear, you are not in control of the vehicle.
Even on level ground where you will not roll when you release the service brakes, the handbrake should be applied as in the event of a rear end collision, you would not necessarily keep hold of the brake pedal, and could roll forward into the car in front, or into oncoming/cross traffic.

I turn my engine off if I think I’m going to be stopped for more than 30 seconds or so, but if I’m the lead car in a queue and I can’t see the cross light then I will often start my engine when I think the light is about to change, rather than waiting until it does. If there are any cars in front of you then you generally have time to start and get moving while the car/s in front get going.
There’s a crossroads in my town which generally has about half a mile of cars queueing for it at peak times, which I generally avoid if possible, but if I find myself in it I’ll leave the engine off until the cars a couple of cars ahead start moving.
I leave the car in first gear with the handbrake on, then when the time comes I only have to press the clutch, turn the key and go.

[Chessic_Sense]

@Morgenstern

Back in the days of carburetors, they used to say one start up equaled 3 minutes of idling. I’m sure that has changed some with the modern computer controlled cars.

I’ve heard 30 seconds, FWIW.

What if something happens and you need to instantly move your car? You’re SOL in that case.

:dubious: Such as…?

@wheresgeorge04

What? No, that’s ridiculous, and certainly worse for the car, the mileage, and the environment.

If only every question could be dismissed so flippantly without citations or argument.

@Quartz

I just put the hand brake on and put the car in neutral.

Why not just use the pedal brakes? Why the hand brake?

@Hairy_Bob

Were you not taught to apply the handbrake every time you come to a complete stop?

:eek: Whaat? You’d be constantly putting it on and off! Who does that?!

[Pai325]

@Hairy_Bob

Were you not taught to apply the handbrake every time you come to a complete stop?

I have never heard of this. Was this something you were taught in driver’s ed?

[Morgenstern]

@Chessic_Sense

:dubious: Such as…?

You hear skidding tires, look in the rear view mirror and see a semi truck impacting cars in line behind you, pushing them in your direction.

You;

a. Start your engine, (hoping it starts this time) put your car in gear and pray you you don’t get pushed into the traffic in the intersection before you can take evasive action.
b. quickly move your car out of the way because your engine was running and your car was in gear.
c. get out and run.

[california_jobcase]

I believe the handbrake on at stops is a British/European thing. Many vehicles in the U.S. don’t have “handbrakes”- they have an extra pedal to the left of the brake or clutch pedal. Makes it nearly impossible to use at a stop in my 5 speed manual transmission truck.

[Morgenstern]

Adding

A lot of environmental organizations advocate the 10-second rule: If you’re going to be stopped for more than 10 seconds, it’s best to shut off your engine. The one exception is when you’re stopped in street traffic—it’s illegal to kill the engine in many states, due to concerns that switched-off cars are more easily rear-ended (especially if an absent-minded driver forgets to restart once the gridlock abates).

Is it more efficient to leave your car idling?

Turning off your car at a stop light may be illegal in your state. Probably a good idea to check that one out before doing it.

[tdn]

@OldGuy

Actually a light that is red for a couple of minutes is very unusual. Someday when you’re stopped at a red light that you consider a long one in your area actually time it. I bet you’ll find that once it gets past 30 seconds, you’re beginning to think it’s a long light. I don’t think you’ll find too many that stay red for even 1 minute.

OldGuy, meet the corner of Comm and Chestnut Hill. Corner of Comm and Chestnut Hill, meet OldGuy. You might as well get aquainted, because you’re going to be together for a loooooong tiiiiiime.

[Kimstu]

The Car Talk guys explain:

RAY: In the old days, when cars were carbureted, there was some truth to the warning against restarting frequently. Because carburetors were so imprecise, they’d essentially dump gasoline into the cylinders whenever you started the car. And some of that gasoline would wash down the cylinder walls, rinsing off the crucial film of oil on there. Then that mixture of gasoline and oil would seep down into the crankcase, diluting the engine oil even further.

TOM: So if you started a carbureted car frequently, oil dilution was a real problem. But these days, with fuel injection, only the exact amount of fuel you need is sent into the cylinders, so there’s no wash-down or oil dilution, no matter how often you start the car.

RAY: So, the only parts that get additional wear and tear from starting the car are the starter and battery. But the effect on the life of the battery will be minimal, because the restarts always occur with a warm engine, which is easy to start. And at least in Toyota’s hybrid system, there IS no starter motor, per se. The hybrid’s electric motor itself serves as the starter motor. And that’s not going to wear out (or at least we hope not!).

TOM: So you CAN save fuel by shutting off your engine. Hybrids are designed to take advantage of that savings. And if you don’t have a hybrid, you can do it yourself. Personally, I think it’s inconvenient to shut off the car at every stoplight. But if you['re] going to be stopped for more than a minute or two, you will save fuel and won’t do any damage to the engine.

[Hairy_Bob]

@Pai325

I have never heard of this. Was this something you were taught in driver’s ed?

Yes, and again more recently when I took my heavy goods license. My instructor taught me to use the hill start procedure every time you start from stationary, that way when you need to do an actual hill start it’s the same as every other time and is no big deal. There is no chance of the vehicle rolling back if you hold the clutch at the biting point whilst you release the handbrake.
I don’t always use the handbrake, if I’m stopping briefly I’ll just hold it on the footbrake but generally speaking it’s handbrake on and in neutral, or in first if I’ve stopped the engine.