# Automotive “Start/Stop” Systems -? **URL:** \ **Category:** Factual Questions\ **Created:** [June 18, 2025, 10:33pm UTC](https://boards.straightdope.com/t/automotive-start-stop-systems/1019820 "2025-06-18T22:33:48Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![FinsToTheLeft](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/finstotheleft/32/2930_2.png) [@FinsToTheLeft](https://boards.straightdope.com/u/FinsToTheLeft)\ **Post date:** [June 19, 2025, 2:19pm UTC](https://boards.straightdope.com/t/automotive-start-stop-systems/1019820/21 "2025-06-19T14:19:34Z")
> [@Thudlow\_Boink](#): > > Surely this is an overstatement? Neither my car nor my SO’s (both from the mid-2010’s) have it. Mid-2010s was a decade ago ---
**Author:** ![Shoeless](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/shoeless/32/7099_2.png) [@Shoeless](https://boards.straightdope.com/u/Shoeless)\ **Post date:** [June 19, 2025, 2:47pm UTC](https://boards.straightdope.com/t/automotive-start-stop-systems/1019820/22 "2025-06-19T14:47:51Z")
> [@LSLGuy](#): > > Substantially all modern cars have it. It’s a very easy way for the car manufacturers to more easily meet the EPA CAFE standards. Y’know, I’ve been thinking about starting a thread about “sport” mode in vehicles and asking why it resets to standard driving mode when you restart the car, but “eco” mode stays in eco mode when restarting. Meeting EPA standards makes perfect sense for that behavior. ---
**Author:** ![Thudlow\_Boink](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thudlow_boink/32/320_2.png) [@Thudlow\_Boink](https://boards.straightdope.com/u/Thudlow_Boink)\ **Post date:** [June 19, 2025, 3:26pm UTC](https://boards.straightdope.com/t/automotive-start-stop-systems/1019820/23 "2025-06-19T15:26:05Z")
> [@FinsToTheLeft](#): > > Mid-2010s was a decade ago Still “modern” compared to 1990s cars. > [@LSLGuy](#): > > Substantially all modern cars have it. It’s a very easy way for the car manufacturers to more easily meet the EPA CAFE standards. If you want to keep driving 1990s cars (or EVs) you’ll be able to avoid it. Otherwise probably not. ---
**Author:** ![Tride](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tride/32/13907_2.png) [@Tride](https://boards.straightdope.com/u/Tride)\ **Post date:** [June 19, 2025, 3:40pm UTC](https://boards.straightdope.com/t/automotive-start-stop-systems/1019820/24 "2025-06-19T15:40:11Z")
The modern systems have gotten pretty sophisticated–they stop the engine at the point of the stroke where compression decreases the load on the starter substantially for restart. The rentals we’ve had with ASS lately have been just fine. ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [June 19, 2025, 3:45pm UTC](https://boards.straightdope.com/t/automotive-start-stop-systems/1019820/25 "2025-06-19T15:45:31Z")
> [@Tride](#): > > The modern systems have gotten pretty sophisticated–they stop the engine at the point of the stroke where compression decreases the load on the starter substantially for restart. In fact, when I had a rental with the ASS feature, it was really quite mysterious how the engine restarted because I never heard the starter crank the engine. Take your foot off the brake, and suddenly the engine was running. I still wouldn’t like it in a new car. It must surely put extra stress on the battery and starter no matter how well designed it is. ---
**Author:** ![Telemark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telemark/32/372_2.png) [@Telemark](https://boards.straightdope.com/u/Telemark)\ **Post date:** [June 19, 2025, 4:11pm UTC](https://boards.straightdope.com/t/automotive-start-stop-systems/1019820/26 "2025-06-19T16:11:42Z")
> [@wolfpup](#): > > It must surely put extra stress on the battery and starter no matter how well designed it is. It really doesn’t in any meaningful way. Warm starts aren’t hard on well designed components. ---
**Author:** ![jjakucyk](https://avatars.discourse-cdn.com/v4/letter/j/3d9bf3/32.png) [@jjakucyk](https://boards.straightdope.com/u/jjakucyk)\ **Post date:** [June 19, 2025, 4:11pm UTC](https://boards.straightdope.com/t/automotive-start-stop-systems/1019820/27 "2025-06-19T16:11:44Z")
> [@wolfpup](#): > > Take your foot off the brake, and suddenly the engine was running. I still wouldn’t like it in a new car. It must surely put extra stress on the battery and starter no matter how well designed it is Technically perhaps, but the battery and starter are specifically engineered for that (except perhaps in Subaru’s case) so you can’t directly compare an ASS system with a non-ASS system because they don’t use the same components. It’s like saying “this semi truck must surely put extra stress on its tires than a compact sedan, no matter how well designed it is.” Except that semi truck has 14 more tires with completely different sizes and tread profiles and weight distribution. ASS is nothing like cold cranking, even in the same car. The engine computer (ECU) is still fully active and knows where each and every cylinder is positioned, the engine is still up to temperature (ASS doesn’t/shouldn’t be active until the engine is warmed up and generally also when the climate control system is mostly satisfied), and the cylinders are all fully oiled. So the amount of additional wear and tear is basically irrelevant because the starter only needs to give the engine the tiniest little kick to get it going again. ---
**Author:** ![Saint\_Cad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saint_cad/32/18907_2.png) [@Saint\_Cad](https://boards.straightdope.com/u/Saint_Cad)\ **Post date:** [June 19, 2025, 4:17pm UTC](https://boards.straightdope.com/t/automotive-start-stop-systems/1019820/28 "2025-06-19T16:17:41Z")
Here is my question about ASS. We are all told that starting your car is the hardest time on your engine. How does ASS avoid this 20 times a drive? Does it still pump oil even when stopped? ---
**Author:** ![Pork\_Rind](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pork_rind/32/111_2.png) [@Pork\_Rind](https://boards.straightdope.com/u/Pork_Rind)\ **Post date:** [June 19, 2025, 4:18pm UTC](https://boards.straightdope.com/t/automotive-start-stop-systems/1019820/29 "2025-06-19T16:18:11Z")
> [@jjakucyk](#): > > the starter only needs to give the engine the tiniest little kick to get it going again. I don’t know how many manufacturers have adopter this system, but as per one of the posts above, there is a variant where the ECU stops the motor with one cylinder just past top dead center. The starter doesn’t engage at all - the spark plug in that cylinder fires, the engine starts running immediately and away you go. ---
**Author:** ![Marvin\_the\_Martian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/marvin_the_martian/32/2898_2.png) [@Marvin\_the\_Martian](https://boards.straightdope.com/u/Marvin_the_Martian)\ **Post date:** [June 19, 2025, 4:23pm UTC](https://boards.straightdope.com/t/automotive-start-stop-systems/1019820/30 "2025-06-19T16:23:11Z")
> [@jjakucyk](#): > > Technically perhaps, but the battery and starter are specifically engineered for that The ASS system in my car has a separate battery. I know this because I just had to replace it. I’ve essentially been driving with ASS since my first hybrid in 2006. The first few times the engine stopped when I stopped caused a little involuntary panic, but I quickly got used to it. The current car is my first true ASS (vs. hybrid) and I don’t notice it at all. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [June 19, 2025, 4:38pm UTC](https://boards.straightdope.com/t/automotive-start-stop-systems/1019820/31 "2025-06-19T16:38:04Z")
> [@Saint\_Cad](#): > > We are all told that starting your car is the hardest time on your engine. It’s mostly bunk. Yes, it theory, there is going to be more wear on an engine when it has been sitting overnight and the oil film on the bearings and rings is the thinnest, but the reality is that the start cycle only rotates the engine a few times, as opposed to the thousands of times each minute (under load) that a running engine goes through. In AS/S, there is still plenty of oil film left on all the parts for when the engine is stopped briefly. ---
**Author:** ![Noelq](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/noelq/32/16438_2.png) [@Noelq](https://boards.straightdope.com/u/Noelq)\ **Post date:** [June 19, 2025, 5:26pm UTC](https://boards.straightdope.com/t/automotive-start-stop-systems/1019820/32 "2025-06-19T17:26:01Z")
I’ve had it multiple times in rental cars, and have hated it each time. ESPECIALLY in lower California. When the ASS turns the car off, it affects the air conditioning, and the car starts to get warm really quick. During a 104 degree heat wave, it was terrible. Started fluttering my foot on the brake so it wouldn’t shut off. ---
**Author:** ![Pork\_Rind](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pork_rind/32/111_2.png) [@Pork\_Rind](https://boards.straightdope.com/u/Pork_Rind)\ **Post date:** [June 19, 2025, 5:45pm UTC](https://boards.straightdope.com/t/automotive-start-stop-systems/1019820/33 "2025-06-19T17:45:19Z")
Both of my cars, if stopped at a long light, will fire the engine back up if the A/C can’t maintain cool temperatures at the vents. ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [June 19, 2025, 5:52pm UTC](https://boards.straightdope.com/t/automotive-start-stop-systems/1019820/34 "2025-06-19T17:52:38Z")
> [@Pork\_Rind](#): > > per one of the posts above, there is a variant where the ECU stops the motor with one cylinder just past top dead center. The starter doesn’t engage at all - the spark plug in that cylinder fires, the engine starts running immediately and away you go. That certainly seemed to be the case in the rental I had. There was no indication of cranking at all, the engine was just instantly running again. OTOH, when stopped at a light, I’ve often heard cars with the ASS feature definitely cranking the engine. ---
**Author:** ![jjakucyk](https://avatars.discourse-cdn.com/v4/letter/j/3d9bf3/32.png) [@jjakucyk](https://boards.straightdope.com/u/jjakucyk)\ **Post date:** [June 19, 2025, 6:16pm UTC](https://boards.straightdope.com/t/automotive-start-stop-systems/1019820/35 "2025-06-19T18:16:40Z")
> [@Pork\_Rind](#): > > …there is a variant where the ECU stops the motor with one cylinder just past top dead center. The starter doesn’t engage at all - the spark plug in that cylinder fires, the engine starts running immediately and away you go. That’s pretty cool. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [June 19, 2025, 7:01pm UTC](https://boards.straightdope.com/t/automotive-start-stop-systems/1019820/36 "2025-06-19T19:01:59Z")
In my view, “modern” anything is last couple design iterations. A model mobile phone is one built in ~2023 or later. A modern car? ~2020 or later. The pace of tech change in those product is just that fast. A “modern” steam iron for clothing? Late 1990s when tip-over sensors and auto shutoff became universal. ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [June 19, 2025, 7:24pm UTC](https://boards.straightdope.com/t/automotive-start-stop-systems/1019820/37 "2025-06-19T19:24:12Z")
> [@LSLGuy](#): > > In my view, “modern” anything is last couple design iterations. Provided you define “modern” as “having the same or similar features as the models currently being sold”. One might equally define a “modern car” as one with an electric starter motor, so you don’t have to hand-crank it. 😉 For me, a modern car is one with a reliable fuel-injected ECU-controlled engine, ABS, cruise control, power door and trunk locks operated from a key fob (a major convenience) and power windows (a minor convenience), and electrically adjustable outside rear-view mirrors. That’s your basic car. My reactions to some of the doo-dads I hear about on “modern” cars vary from “that’s nice, but why would you really need that?” to “that’s stupid, why on earth would you want that?”. And for me, ASS falls into the latter category. The kind that cranks the engine every single time you stop is right out for me. The kind that auto-starts without needing the starter motor is marginally more acceptable, but I’d worry that it’s the kind of complexity that is subject to failure. The best safeguard against having fancy components fail is the principle that components that you don’t have can’t fail. For someone like me where a car is just transportation, but very important for that purpose, reliability is everything. ---
**Author:** ![Tride](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tride/32/13907_2.png) [@Tride](https://boards.straightdope.com/u/Tride)\ **Post date:** [June 19, 2025, 7:41pm UTC](https://boards.straightdope.com/t/automotive-start-stop-systems/1019820/38 "2025-06-19T19:41:37Z")
But if it’s solely the ECU then it’s not complex. Reminds me when some one at Bombardier said to themselves “Wait, don’t 2 strokes run in reverse just fine if you adjust the timing?” And all of a sudden snowmobiles had reverse with no gears, just an electronic timing change. Simple, no moving parts, kinda genius. I mean, seeing a 26% efficiency gain at the high end is HUGE. Automakers are chasing fractions of percentage points with things like lighter oil, so this a major, major gain. Plus it has the advantage of working best in heavy traffic which occurs where pollution tends to be highest also. ---
**Author:** ![Pork\_Rind](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pork_rind/32/111_2.png) [@Pork\_Rind](https://boards.straightdope.com/u/Pork_Rind)\ **Post date:** [June 19, 2025, 9:06pm UTC](https://boards.straightdope.com/t/automotive-start-stop-systems/1019820/39 "2025-06-19T21:06:51Z")
> [@wolfpup](#): > > For someone like me where a car is just transportation, but very important for that purpose, reliability is everything. I mean, I get your point. But I just don’t think the automatic start stop is any kind of a reliability nightmare. I know my small sample is just anecdotal evidence, but thinking of the three cars in the last 10+ years that I’ve had that have had that function, I have never had any repair issues related to it. But also keeping those three cars in mind, the repair issues that I’ve had, maybe I can count them on one hand? And none that have left me stranded. As far as I can remember, the last time I was stranded by a gas car that was not accident related damage was back in the early 90s. ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [June 19, 2025, 10:26pm UTC](https://boards.straightdope.com/t/automotive-start-stop-systems/1019820/40 "2025-06-19T22:26:57Z")
> [@Saint\_Cad](#): > > We are all told that starting your car is the hardest time on your engine. True. But only when the engine block is cold. It has to do with the gasoline contaminating the oil. @Machine_Elf gives an excellent explanation [here](https://boards.straightdope.com/t/cold-start-vs-warm-start-for-cars/674556/7). [Previous page](https://boards.straightdope.com/t/automotive-start-stop-systems/1019820.md?page=1) [Next page](https://boards.straightdope.com/t/automotive-start-stop-systems/1019820.md?page=3)