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I drive a 2017 VW Polo 1.0L. I use the car for primarily short journeys with the occasional motorway run. The car has a start stop function but I am skeptical of the benefits.

Will it be a useful feature for somebody who does mostly short journeys (under half hour)?

  • depends on what you consider useful... – Solar Mike Sep 29 '17 at 8:56
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    If you're a getaway driver, then keeping the engine running is certainly useful while your mates rob the bank. On the other hand, it draws cops attention, as idling engine is prohibited in many traffic codes... Bummer! – Agent_L Sep 29 '17 at 14:41
  • Depending on the implementation, you will have to alter your driving style to get the most out of the system - I often put a car with automatic transmission manually in neutral, so that releasing the brake for a smooth stop does not unnecessarily start the engine. – Sanchises Sep 29 '17 at 20:14
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Generally, these systems don't activate until the engine is warm, so you probably won't see it for the first 5-10 minutes of your journey - of course it largely depends on the nature of your journey as to whether that's useful or not, plus, as Solar Mike says, what you consider useful.

For example, if your half-hour journey is 20 minutes pottering through the suburbs, then 10 minutes sitting in traffic as you approach your workplace, then it will probably be useful as it will cut in as you sit in the traffic, helping to reduce your emissions (and fuel cost!)

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    +1 in my experience the VAG implementation of Stop/Start is very good at only doing it when it's actually worth it and the sort of journey you describe is the exact sort of thing that the system is designed for. – motosubatsu Sep 29 '17 at 9:38
  • So would you say that the reduced emissions and fuel costs are a worthy pay-off of possible wear to starter motor / battery etc.? – Joe Sep 29 '17 at 10:08
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    @Joe the system is designed so that the engine stops in the easiest position to restart it. Plus the starter and battery are both beefed up over non-stop/start versions to handle the extra use so they won't wear out any quicker than the equivalents either so in general yes it's basically all upside to you the owner. – motosubatsu Sep 29 '17 at 12:34
  • If you live somewhere where AC is needed, then depending on how it's implemented, this feature either won't engage at all (because the AC is on) or it will prevent your AC from working until you turn it off. In either case it's not useful or helpful to you. Likewise for heating - your heat will quickly go away without the engine running. – R.. Sep 29 '17 at 17:45
  • @motosubatsu But then again, they will wear out a lot less quick than their conventional counterparts if you never use them. – Sanchises Sep 29 '17 at 20:15
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When I had about 60 000 km on my 2011 Toyota Yaris with start/stop, the start/stop meter showed the engine had been stopped for 14 hours. So, 300 000 km, a useful lifetime of a car, means the engine will be off for 70 hours. At 0.7 l / hour, this is 49 liters of saved fuel. Depending on the fuel costs, the expense may vary, but it'll probably be below 100 USD. A new battery costs 50 USD, a new starter motor far more than that.

Based on this, I would turn off the start/stop system if there's the possibility to turn it permanently off. The extra wear on precious components (battery, starter) more than outweighs the benefits obtained. Sadly, my 2011 Toyota Yaris had the possibility to turn it off only for the current trip and it would be automatically turned on for the next trip.

Also, consider this: most start/stop cars cannot use the heater or AC when the engine is stopped.

My current car, a 2016 Toyota RAV4 hybrid, also has the capability to stop the engine and in this case it is very useful as it can even turn off the engine when in motion, powering the car only from the battery. Hybrids are in a league of their own. Both heating and AC work when the engine is stopped due to electric pumps and compressors.

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    Wait, but did you habitually turn the start/stop system off? If it was only running when you forgot to turn it off, and you usually remembered, it wouldn't be surprising if it hadn't been used very much. Also, you don't say what kind of driving you do. If you mostly drive on highways, you wouldn't expect to get any benefit from this kind of system. – David Richerby Sep 29 '17 at 13:36
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    But what is the chance of the starter motor failing prematurely due to having to start the engine a bit more often? Only when you know that, you can say if start/stop is beneficial or not. You've also neglected two additional benefits: those 14 hours the engine has been stopped, is 14 hours the engine would have run stationary, so you've reduced your engine wear (albeit by a small amount). Plus the environmental benefits of not producing combustion gases while sitting in traffic. – Hobbes Sep 29 '17 at 13:44
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    On the Volkswagen system, a heavy duty starter motor and battery are fitted with a far longer duty cycle than the standard cars. – Steve Matthews Sep 29 '17 at 14:14

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