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I recently purchased a used 2012 Volvo XC70. It has a diesel engine and the start-stop function. Both the salesman and later my mechanic told me the same thing - this feature wears down the starter quickly and I'm better off by turning it off. However I'm a bit skeptical about this and suspect that they simply might have some old habits.

I googled around about this but couldn't find much solid information. Some sources claim that the start-stop starters are different than normal starters and are designed for such loads. Others say that the starter will wear down more quickly. So which is it? Does the start-stop function wear down a car's starter faster, or is the starter specially built for this and will not need replacing more often (if ever)?

Some more notes:

  • While I am, of course, most interested about my specific car, this site welcomes more generic questions if possible. So ideally I'd also like a more generic answer, not tied to a specific make or model. However I can totally understand that for different manufacturers the answer may vary, so - the more information, the better.
  • I'm not questioning whether the system actually achieves any fuel efficiency. That's a separate question that I'll seek to answer with my own observations in the coming months.
  • Neither am I asking about battery wear. Obviously such a system places greater load on the battery, which is why AGM batteries tend to be used. For some cars (mine included) there's even a smaller secondary battery just for the start-stop system. It's understood that this battery will most likely wear down much faster (probably lasting only a couple of years), however replacing that is much easier and cheaper than replacing the starter, so it's not such a big problem.
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As you stated hybrid technology varies by model and brand. I will answer in generalities. The manufacturer warranties the starter for at least 36,000 miles and in some cases 100,000 miles. They don't want to replace components for free. For the most part components are designed to last past the warranty. The start-stop function is more complex than just shutting off the motor and restarting it. The hybrid starter motor is larger. In some cases it is actually a starter/alternator and is belt driven. This eliminates the potential for wearing out the flywheel. In some models the engine is stopped in a specific point in the combustion cycle. This allows the motor to start with a minimum amount of cranking, saving the starter and making the process seem seamless.

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    "Hybrid"? I thought the word "hybrid" meant a car with both an electric motor and a conventional one, where you can switch between what you use. This isn't what I meant. What I meant was cars with only a conventional engine (either diesel or petrol), but which stops the engine at red lights and then restarts it once you touch the controls again.
    – Vilx-
    Commented Dec 31, 2019 at 11:52
  • I believe Mike's was referring to hybrid technology and not necessarily hybrid vehicles. I am very interested in this topic and would also like to hear some real world information on these systems. Specifically on maintenance and durability.
    – Jupiter
    Commented Dec 31, 2019 at 13:15
  • When only the start -stop feature is installed it is sometimes referred to as passive hybrid technology. It doesn't have electric drive motors for the wheels.
    – mikes
    Commented Dec 31, 2019 at 13:51
  • Some manufacturers refer to start stop as "microhybrid" I agree with mikes, the belt driven starters are not turning the flywheel directly and can therefore even restart an engine while coasting.
    – AnyOneElse
    Commented Jan 30, 2020 at 15:06

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