# Why do new cars shutoff at intersections? **URL:** \ **Category:** Factual Questions\ **Created:** [February 17, 2020, 4:14am UTC](https://boards.straightdope.com/t/why-do-new-cars-shutoff-at-intersections/848058 "2020-02-17T04:14:01Z")\ **Posts on this page:** 8\ **Page:** 4
**Author:** ![Misnomer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/misnomer/32/14897_2.png) [@Misnomer](https://boards.straightdope.com/u/Misnomer)\ **Post date:** [February 27, 2020, 9:52pm UTC](https://boards.straightdope.com/t/why-do-new-cars-shutoff-at-intersections/848058/61 "2020-02-27T21:52:37Z")
> [@TheCuse](#): > > My 2019 Cherokee has a button I can hit to override the start-stop system, but I have to hit the button every time I first start up. > [@Riemann](#): > > Yes, they are all like this. The reason is that the EPA will only give full credit for the improved efficiency if they are designed this way with a “non-persistent” off switch. My 2020 BMW M240i has a button to override the start-stop, and it’s persistent (thank GOD). If I haven’t shut the car off myself, I find any lack of engine noise disturbing. > [@Capn\_Carl](#): > > I’ve driven a few rental cars with auto shutoff. I don’t see what the objection is. It’s barely noticeable if there’s any noise from the radio or conversation. What, do you only rent hybrid/electric vehicles? :dubious: 😉 I \*always \*notice an engine turning off. ---
**Author:** ![Bijou\_Drains](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bijou_drains/32/2814_2.png) [@Bijou\_Drains](https://boards.straightdope.com/u/Bijou_Drains)\ **Post date:** [February 27, 2020, 10:43pm UTC](https://boards.straightdope.com/t/why-do-new-cars-shutoff-at-intersections/848058/62 "2020-02-27T22:43:29Z")
I thought this was only in hybrids but I see that’s no longer true. ---
**Author:** ![Pantastic](https://avatars.discourse-cdn.com/v4/letter/p/3bc359/32.png) [@Pantastic](https://boards.straightdope.com/u/Pantastic)\ **Post date:** [February 27, 2020, 11:06pm UTC](https://boards.straightdope.com/t/why-do-new-cars-shutoff-at-intersections/848058/63 "2020-02-27T23:06:52Z")
> [@bump](#): > > The old carburetor days rule of thumb was that turning the engine off/on was roughly equivalent to idling for one minute, IIRC. So if you thought you’d be sitting still for more than a minute, it was most efficient to turn it off, but if you thought you’d be sitting still less than a minute, it was most efficient to just idle. But doesn’t turning off the engine on a carburetor risk vapor lock, at least on older models? I was taught not to turn off a car unless it was going to be a long enough stop for the engine to cool off, and I definitely remember seeing the occasional person who shut off their car while waiting for a bridge get stuck unable to restart. ---
**Author:** ![WildaBeast](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wildabeast/32/6_2.png) [@WildaBeast](https://boards.straightdope.com/u/WildaBeast)\ **Post date:** [February 27, 2020, 11:41pm UTC](https://boards.straightdope.com/t/why-do-new-cars-shutoff-at-intersections/848058/64 "2020-02-27T23:41:24Z")
> [@Misnomer](#): > > My 2020 BMW M240i has a button to override the start-stop, and it’s persistent (thank GOD). If I haven’t shut the car off myself, I find any lack of engine noise disturbing. IIRC, BMW, Porsche, and other performance oriented makes decided it’s better for their business to just pay a fine to the EPA every year for not meeting CAFE, than to dilute their brand by offering small, fuel efficient cars required to meet CAFE standards. So it wouldn’t surprise me if BMW doesn’t care if they don’t get credit from the EPA for improved fuel efficiency by making the auto-stop override persistent. ---
**Author:** ![Corry\_El](https://avatars.discourse-cdn.com/v4/letter/c/ecae2f/32.png) [@Corry\_El](https://boards.straightdope.com/u/Corry_El)\ **Post date:** [February 28, 2020, 4:39am UTC](https://boards.straightdope.com/t/why-do-new-cars-shutoff-at-intersections/848058/65 "2020-02-28T04:39:09Z")
> [@WildaBeast](#): > > IIRC, BMW, Porsche, and other performance oriented makes decided it’s better for their business to just pay a fine to the EPA every year for not meeting CAFE, than to dilute their brand by offering small, fuel efficient cars required to meet CAFE standards. So it wouldn’t surprise me if BMW doesn’t care if they don’t get credit from the EPA for improved fuel efficiency by making the auto-stop override persistent. For BMW it’s varied over time and by model (besides what country the car is sold). Also some cars have it coded at the dealer to ‘remember last setting’, though it comes from the factory coded to reset to ‘on’ each time you start the car. Also I’ve read on owner forums the rumor at least they are going to eliminate the button on some models so you can’t turn it off even for that drive. In terms of own cars, in 2015 F30 328i the start/stop would reset to ‘on’ and drive mode ‘comfort’ each time you started the car. You could either turn off start-stop or switch the drive mode to ‘sport’ and it wouldn’t be on either way, until next time you started up the car (yourself I mean, not including the start-stop doing it). 2018 F87 M2 it remembers the last start-stop setting in all modes. If you turn it on it’s on next time you start up regardless of mode, likewise if you turn it off it’s off next time you start the car. Again it doesn’t bother me when it’s on and I’m skeptical of people claiming it has any real effect on component life. Again maybe in exceptional case of really pushing the car on an uphill stretch of winding road I’d want to turn off start stop in case of the rare stop to avoid going from heavy load to engine stop. But in stop and go local driving, topping out at maybe 100 lb-ft on the torque gauge (v 390 top), I doubt it. ---
**Author:** ![aruvqan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aruvqan/32/2891_2.png) [@aruvqan](https://boards.straightdope.com/u/aruvqan)\ **Post date:** [February 28, 2020, 6:05am UTC](https://boards.straightdope.com/t/why-do-new-cars-shutoff-at-intersections/848058/66 "2020-02-28T06:05:07Z")
> [@Absolute](#): > > Together, this is why I think EVs are going to take off much faster than anyone thinks, particularly in the premium / “entry luxury” market ($30,000+). They’re completely quiet and smooth, and respond instantly and linearly. It’s a vastly more pleasant experience than a small turbo 4-cylinder. Perhaps in more populated areas … I have land for a retirement house in a _very_ rural area of western Nevada - the ‘town’ has a convenience store with gas pumps, 200 people and about 20 000 cows, and assorted feral donkeys and horses. The nearest town is 45 miles away, the nearest anything is 45 miles away. [Reno is 250 miles northish, Las Vegas is 250 miles southish] I don’t know about you, but I refuse to have a vehicle that I can’t carry a spare jerry can of fuel in case I run out of gas. I want something I can dependably go 40 or 500 miles on day or night, and top off a simple fuel tank and drive another 400 or 500 miles day or night. If I had to keep tracking down and figuring out how to source a power point to jack into, I would go nuts. Look, not everybody lives in the classic urban/suburban 5 miles to the next town areas. Some people are more rural than our new place. ---
**Author:** ![Hampshire](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hampshire/32/4887_2.png) [@Hampshire](https://boards.straightdope.com/u/Hampshire)\ **Post date:** [February 28, 2020, 4:33pm UTC](https://boards.straightdope.com/t/why-do-new-cars-shutoff-at-intersections/848058/67 "2020-02-28T16:33:53Z")
> [@DrCube](#): > > The only problem I foresee, and I know I’ll catch flak for this, but on cold mornings I want to start my car and let it run for five or ten minutes to warm up. It allows me to enter the vehicle without being miserable, it lets me clear the windshield with a brush instead of a scraper (or even just a flick of the wipers), and as far as I’m concerned it isn’t inefficient at all. For those few minutes I don’t want the car to take me anywhere, I want it to be a space heater, and space heaters are always 100% efficient. MPG can wait until I’m on the road. > > I’ve never driven a car that shuts off automatically, but as long as I can override that feature until the car is warm, I’m okay with it. Otherwise, we’ll have a problem. I can’t speak for all cars with the shut-off feature, but my Tiguan will not turn off the engine if I have the cabin thermostat set to a certain temp and the cabin temp falls out of that range. For example, I have the cabin temp set at 70 degrees, the cabin is at 70 degrees, the outside temp is 10 degrees. I pull into a drive-thru line and sit. Car engine turns off. Cabin temp dips below 70 degrees. Engine automatically starts again to start heater to warm up the cabin. This also works in the summer when using the A/C. If I have the cabin set at 70 and the engine turns off, as soon as the cabin hits 71 the engine will start again to kick on the A/C. ---
**Author:** ![Procrustus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/procrustus/32/2994_2.png) [@Procrustus](https://boards.straightdope.com/u/Procrustus)\ **Post date:** [February 28, 2020, 4:39pm UTC](https://boards.straightdope.com/t/why-do-new-cars-shutoff-at-intersections/848058/68 "2020-02-28T16:39:26Z")
> [@aruvqan](#): > > Perhaps in more populated areas … I have land for a retirement house in a _very_ rural area of western Nevada - the ‘town’ has a convenience store with gas pumps, 200 people and about 20 000 cows, and assorted feral donkeys and horses. The nearest town is 45 miles away, the nearest anything is 45 miles away. [Reno is 250 miles northish, Las Vegas is 250 miles southish] I don’t know about you, but I refuse to have a vehicle that I can’t carry a spare jerry can of fuel in case I run out of gas. I want something I can dependably go 40 or 500 miles on day or night, and top off a simple fuel tank and drive another 400 or 500 miles day or night. If I had to keep tracking down and figuring out how to source a power point to jack into, I would go nuts. > > Look, not everybody lives in the classic urban/suburban 5 miles to the next town areas. Some people are more rural than our new place. The comment > [@](#): > > this is why I think EVs are going to take off much faster than anyone think does not mean that they are ideal for everyone. EVs can take off very fast even if the 200 people in your small village have good reason to prefer ICE vehicles. [Previous page](https://boards.straightdope.com/t/why-do-new-cars-shutoff-at-intersections/848058.md?page=3)