Car Advice

Myth-busting: Does stop-start damage your engine?

Plenty of people will tell you what they like and don’t like about stop-start systems. But, does stop-start damage your engine?

PLENTY OF OPINIONATED writers will tell you how stop-start is all about carmakers gaming the system in lab-based fuel economy tests, and to some extent it is, but there’s more to stop-start than that. Sit back and let uncle Isaac learn you…

What’s the history of stop-start?

It was the 1980s, an age of big hair, great movies (Highlander, Ghost Busters, Top Gun, Indiana Jones, Star Wars…) and innovation in cars. Long before some ‘rogue’ Volkswagen engineers decided to game the system in California and cause ‘dieselgate’, some Volkswagen engineers invented stop-start.

Or, at least, it was Volkswagen that first applied the idea to production vehicles. Stop-start was a suite of technologies the brand launched under its Formel E (Formula E) brand. Think of it as BlueMotion before BlueMotion. Under Formel E, the relevant Passat, Polo and Golf (be it petrol or diesel) would be fitted with aerodynamic bits and bobs, tweaked transmissions which featured a tall top gear, (called an e gear) for fuel saving while running at a constant speed on the highway. The Formel E kit also included a gear shift indicator which via a yellow light on the instrument panel would advise when to shift up a gear for maximum efficiency.

But the main piece of kit was stop-start which you would activate by pressing a button on the dash and then pressing it again to turn the engine back on, or when you slotted first gear in a manual car.

Unfortunately, stop-start didn’t catch on. Not in the 1980s, anyway. It reappeared in the 1990s in hybrid cars and wasn’t until 2013 that it really became a thing in cars. Yes, really.

So, what is stop-start?

Once the vehicle is stationary the engine is killed until the driver either dips the clutch and slots a gear (on a manual vehicle; to activate it the driver needs to put the transmission into neutral) or you come off the accelerator pedal and onto the brake and stop the car (on a vehicle with an automatic transmission). In most applications, the stop-start defaults to on but it can usually be deactivated via a button on the dashboard; although it will switch back on every time the car is turned off and on again with the key. The thinking behind it is that it saves fuel and emissions that might otherwise be generated while the vehicle is idling away at a set of traffic lights.

It’s worth remembering here that stop-start will only work when conditions are ‘just right’, meaning, if it’s too cold or too hot and the HVAC is working overtime to keep your warm or cool then the stop-start will switch off the engine but then a split-second later turn it back on again to prevent the battery from being overloaded. And it’s rare, even when conditions are right, that a stop-start system will keep your vehicle’s engine switched off for more than 90 seconds.

Does stop-start cause premature wear and tear?

The widespread application of stop-start has only been possible because of improvements in things like battery technology, bearings, oils and control systems in vehicles. See, asking an engine to stop and then start again places strains on components. Indeed, if you took a starter motor from the 1990s and looked at one from today, the modern starter would be much stronger capable of handling up to 500,000 cycles in its ‘lifetime’ – the older starter would have only been designed to handle around 50,000 start cycles. All sorts of things are different, from the type of bearings used, to the long-life brushes, the way the solenoid works, the wiring (beefed up). The aim is to make it easier for the starter motor to do its job.

The same with the battery which is now a much stronger thing than it was in the 1990s, and that’s because when the engine’s stopped, but we still want to keep our lights on and listen to music and run the heating or cooling, and then start the engine when the lights turn green. Beyond a beefed-up battery and wiring harness, some system utilise a separate battery for restarting the engine while the main battery worries about everything else, and some use a capacitor that stores a charge to jolt the starter motor. And then there’s slicker, stickier engine oil that will stay on the moving parts when the engine is stopped for longer, and bearings which are now slipperier via lubrication but also in construction.

Practical Motoring spoke with the technical boss at a leading car maker who said that stop-start doesn’t cause additional wear and tear on an engine but that the owner must adhere to the recommended service schedule and use the manufacturer’s recommended oil. “Using cheaper oils can cause more damage to your car’s engine than anything else,” he told Practical Motoring. “Operational stop-start causes no wear and tear at all; wear and tear at cold start-up is a thing, though,” he said.

Does stop-start save you money or fuel?

Well, this is the question that generally send the internet into meltdown. It’s a personal thing, I think. For me, stop-start saves me maybe a couple of cents worth of fuel a week, but that’s simply because of the driving I do. Long stints between stops. But, if you’re in stop-start traffic then it’ll be more active and save you a little more than it does me.

It does mean there are less tailpipe emissions, but when you consider the vehicle will only stop itself for a maximum of up to 90 seconds in best-case scenarios then the overall saving can be measured in cents and a fistful of dollars only over time, rather than hundreds and thousands of dollars.

In terms of fuel, the savings will be about the same… it’s a tiny bit here and a tiny bit there. And while some will suggest that’s a good enough reason to switch off stop-start, I’d argue that the ability to save every bit of dead dinosaur essence you can is worth it.

Is the point of stop-start to save money and fuel or allow car makers to make a better fuel economy claim?

Well, this depends on who you listen to. Yes, the idea behind it is to save money and fuel, but some argue it’s so that car makers can game the system; meaning, when it comes to the lab based fuel consumption test. You can read more about how that works HERE, but in a nutshell a car is plonked onto a rolling road and run for around 20 minutes in two blocks of 10 minutes. A large chunk of that simulation is intended to recreate stop-start running and so some argue that those with a stop-start system gives an advantage to those that don’t. But that’s only sort of correct. See, most, if not all new cars now come with stop-start as standard, especially in the most competitive segments, and because stop-start will only idle-stop the car for a maximum of around 90 seconds the advantage would be minimal.

The usability of stop-start…

It used to be that these systems were very rough. Indeed, they were so rough that in the US, people complained about the BMW 3 Series when stop-start was first introduced on it that it was recalled and the system redesigned. And I’ve driven vehicles where you can take your foot off the brake and count to three before the thing fires back into life.

Stop-start systems, be they on a petrol or diesel vehicle, are, generally speaking, so smooth you’ll barely notice when the thing’s shutdown and, by the time your foot has come off the brake pedal the car has started again and you’re off and running. Some systems even respond to a jink of the steering wheel. Or there are those that are clever enough to determine when you’ve slowed down almost to a complete stop but have changed your mind and jumped back onto the throttle again… even though the system has started its stop cycle, it’s able to cancel that in a split second based on your throttle application and keep you moving; Subaru’s stop-start system does this very well, for example.

In the end

Stop-start is a clever system which while it won’t save you huge amounts of fuel or money isn’t necessarily a bad thing, because every little bit helps, right. But, if you’re one of these people that absolutely abhors stop-start then you can, in most cases, just turn it off – Just remember you’ll have to do this every time you get in your car because the default is for it to be active.

Question: Does your car have stop-start? What do you think, and do you use it?

Find the best demonstrator car deals for Practical Motoring readers around Australia on our Live Deals website. 


  1. Dale
    January 19, 2018 at 9:01 am — Reply

    So what your saying is, the system won’t save you money or fuel? The system only works in ideal conditions (like when is it ever hot in Australia)? It will only stop for 90 seconds at a time, so what happens in very heavy traffic jams, does it start/stop several times if you are stationary for 5 minutes? and no matter how you phrase it, there is always a delay for the restart and even on most current models the refinement of the restart is terrible.
    So wheres the benefit here?

    • Scott M
      April 21, 2020 at 10:41 am — Reply

      My 2019 Subaru Forester has auto stop/start, and the jolting restart is extremely annoying. It’s also dangerous to be paused if there is a need to move away from the stop quickly to avoid collision or other danger. My other car is a hybrid and does not have these issues because the motor initially moves the vehicle while starting the gas engine. I decided to test the fuel consumption on my Subaru for 30 days with and 30 days without Auto Stop/Start. I drove about 1,000 miles each month. My Southern California commute includes both cross town traffic with many stoplights and congested stop-and-go freeways, which should make the most of Auto Start/Stop. I got slightly better fuel economy with the Auto Stop/Start disabled. 21 MPG with the feature On and 22 with the feature off. Without a fully controlled test, it’s not realistic to claim that Auto Stop/Start causes more fuel consumption, but it is safe to say that AUTO START/STOP ABSOLUTELY DOES NOT IMPROVE MPG ENOUGH TO BE A BENEFIT TO YOU. After my test, I did some research because I wanted to understand why a car manufacturer would force such an annoyance on people without providing a benefit. I found that the feature improves emission ratings which equate to more money for the car company from government programs, and thus more profit. I bought an “Autostop Eliminator” module, and highly recommend that anyone else annoyed by this disservice to consumers do the same.

  2. Michael Barron
    January 19, 2018 at 6:21 pm — Reply

    We recently bought a Mazda 3, and if the car was mine, instead of my wife’s, I would turn the stop/start off as I think it is a waste of time for cars in Cairns, because of the lower traffic levels and the hot weather.
    What really annoys and disappoints me is the Mazda 3 startup procedure. On starting the car the engine revs to 1500 rpm for about 20 seconds, then slowly drops back to an idle speed of 800 rpm. The Mazda people told me that this is to warm the car up quicker, but as your story above notes, most engine wear occurs at cold startup, and no-one in the world could convince me that revving the engine to 1500 rpm from cold doesn’t contribute to increased engine wear.
    Of course the numerous times that we test drove the cars this didn’t happen, as the cars were already warmed up from being driven that day. I honestly would not have bought a Mazda 3 if I was aware of this, and I really feel like I have been conned. Not happy Mazda.

  3. Terry Panitz
    January 19, 2018 at 8:15 pm — Reply

    Peugeot have dropped it on Australian spec cars even after beefing up the starter system. The cars I driven, including the Subaru Forester & Nissan Note manual (Europe) were OK. Some are still slow to get away. I can see the advantage in long traffic jams in clean air and reduced fuel consumption, but what about air-conditioning in Australia’s warmer/hotter conditions, it runs all the time?

  4. B-17
    January 19, 2018 at 9:04 pm — Reply

    yes, my car has stop-start. (new Golf Alltrack)
    No, I don’t use it. I turn it off. I forgot a couple of times, and it wasn’t a problem, it was unobtrusive.
    But you won’t convince me that it doesn’t prematurely wear out starting components. For little gain.
    Front and Rear Cross Traffic Alert would have been a lot more useful, and a power tailgate.
    Both of which are inexcusably left off the Alltrack.
    As is fresh air ventilation without the climate control switched on.
    But I suppose i shouldn’t complain too much. I bought the car. And the windows do open.

  5. Monty
    January 20, 2018 at 9:25 am — Reply

    Yes and yes. It works fine. Any delay is microscopic and is only a concern if I am the first car at the lights.

  6. trackdaze
    January 20, 2018 at 9:58 am — Reply

    48v mild hybrid will solve much of the drawbacks of stop start and improve fuel economy by ~10%

  7. John John
    January 20, 2018 at 11:25 am — Reply

    Hard to argue an overall saving when the extra cost of a new battery suitable for stop-start equipped cars may wipe out any savings stop-start may have made.

    I just don’t like stop-start overall. My Mazda has it, so far I’ve “saved” enough fuel to run 20 kilometres, and it took me 11,000 km to do that. Let’s be generous and say that’s 2 litres of petrol saved, $3 or so. But my car’s a manual, and stop-start kicks in less frequently than in an auto (and yes, despite not really liking stop-start I usually leave it switched on).

    Having said that, I do like some aspects of stop-start. When stopped at lights that I know are going to be red for a while it’s nice to have the engine switch itself off, you get a bit of peace and quiet.

  8. gab4moi
    January 20, 2018 at 8:48 pm — Reply

    Yet another reason I opted for the I30 SR!

  9. Fred
    January 23, 2018 at 12:09 am — Reply

    I get it,but what about safety.Engine off,gear in park,look in the mirror…this guy will never stop in time,i am about to be rear ended.In other words i have no control.If the engine is running and the gearbox is in gear..,split seconds count here,i can try to get out of the way,or at least try to do something.I am in control.

    • DJR
      January 24, 2018 at 8:56 am — Reply

      Exactly, Fred. I bet this situation wasn’t thought of.

  10. DJR
    January 24, 2018 at 8:55 am — Reply

    Own a NXLexus, hate the stop start system, first thing I do after start is to turn it off, for the thimble of fuel saving, the vehicle tells me how much fuel it’s saved me, it’s not worth the trouble.
    Not so good in traffic when you have to wait for a restart to leave the traffic lights, wish I could permanently turn it off.

  11. Simon
    April 30, 2019 at 1:32 am — Reply

    It might not save you much money on fuel but it’s much more pleasant for pedestrians walking alongside a traffic queue if the vehicles have stop-start enabled.

  12. Scott
    January 9, 2020 at 8:19 am — Reply

    It isn’t just hard on the starting parts, you are taking off from a dead stop right after the engine is started. That’s demanding a lot of power from the engine who’s oil isn’t circulating yet. Over and over. Typically I let a engine warm up a bit at idol before demanding a bunch of power from it. I think much of the push behind this system is to require auto makers to buy deep-cycle batteries, Johnson Controls batteries in particular, who claim the AC still runs with the engine off in their promo video. Not possible, the AC is belt driven by the engine. I’m starting to think a second reason behind this is a move to disposable cars because the piston rings are going to be shot in I’d guess 3 – 5 years, then the cars will be smoking so much they won’t pass emissions testing.

  13. Dan
    April 8, 2020 at 7:27 pm — Reply

    Its not about the battery, who cares for battery. Its not about starter, who cares about a starter, its not a big deal if it goes prematurely. They last 20 30 year anyway. The wires does not need to be beefed up and they are not compared to cars without start stop. Its about turn off hot engine, stoping circulating oil and water, its about hot spots here and there. Inside the engine head, engine block and its about turbocharger. You just dont want to engine to stop sudenly when is very hot in summer in the city or after spirited driving. That s not good for any engine – period. If the engine have better crucial parts (but they don t) that does not change the fact that without using start stop, theese parts will last longer. How long, it depends on many factors. When you turn off hot engine the temperature inside engine will rise. That s pure physic. And then there is a turbocharger. Stoping engine suddenly when turbo is at its peak temperature is not smart move to do.

  14. Dr Bob
    April 22, 2020 at 7:19 am — Reply

    We only do short runs in our Mazda3, and I-Stop only activates two or three times during the average journey. Annoyingly, it cuts the engine when stopping briefly in the driveway to unload passengers or shopping items.

    I’ve simply disabled the system by adjusting the “service” switch in the engine compartment.

    There’s a scam operating concerning the battery requirement for i-Stop; Mazda will tell you that you need a special battery, and wants to sell you a very expensive replacement. When I need a replacement, I’m just going to get a good quality standard battery.

  15. Dave D
    May 21, 2020 at 11:49 pm — Reply

    According to ASME, 85% of engine wear occurs during starts as the oil film on rotating and rubbing surfaces doesn’t exist. Start stop has to cause extra wear because the oil film takes time to form after the oil pump starts. An auto manufacturer doesn’t care because it will be out of warranty when the engine fails, but it will fail earlier than an engine without start stop. Also, having a $50k plus vehicle using start stop to save a few dollars a year in fuel costs is pennywise pound foolish. It is a dumb illogical unscientific feel good climate change response.

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Isaac Bober

Isaac Bober