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Chances are that if you bought a new car in the last couple of years or so, one of the modern technology features present on it makes your engine shut down everytime you stop for more than 1-2 seconds, sometimes even less

Called “start-stop,” the technology is heralded as the next best thing in the automotive industry since the invention of windshield wipers or rearview mirrors. Some carmakers also call it “micro-hybrid technology” for reasons that I will soon explain.

In theory, there are nothing but upsides to start-stop systems, whether you like them for the lower fuel costs or for the fact that they mildly contribute to fewer emissions inside the city you're living and using them in.

As the official nomenclature suggests, a start-stop system simply shuts off your car's internal combustion engine (ICE) instead of leaving it idle during prolonged stops. It then almost miraculously starts it again the moment you either get your foot off the brake or press the clutch to select the first gear in a vehicle with a manual transmission.

Newer vehicles fitted with the system make the transition from “off” to “on” almost seamless and in a fraction of a second, less time than the blink of an eye.

Since multiple engine starts in a short amount of time would put a lot of stress on conventional starter motors, to the point of destroying them prematurely, cars that have “start-stop” use heavy duty starts, specifically designed for the job at hand.

They also have better batteries, which in certain vehicles can also be charged via regenerative braking, thus making them micro-hybrids. In the overall hybrid cars scheme, micro-hybrids are just below mild-hybrids, and two steps bellow full hybrids.

Some carmakers have resorted to a so-called integrated starter-alternator (ISG), while others only use a heavy-duty starter motor and call it a day. Both versions of a start-stop system work in similar ways and achieve the same thing, though, better fuel economy in stop and go traffic.

All is fine and dandy, especially since the technology is not expensive and has a much lower weight disadvantage compared to what is found under the hood of a full hybrid. But is everything as fantastic as all these carmakers are making it seem?

Modern cars have so many electronics and power consumers that they need a lot of continuous current to keep working, especially when the ICE, the main “distributor of volts to the battery” is shut down. Lights, climate control, audio system, not even the airbags will work if there is no power, which is why in cars with start-stop the battery is put through much higher strain.

You'll probably say “Hey, Alex, stop smoking that, carmakers have thousands of engineers that have already thought about what you're implying!” Sure, I bet they did, but that doesn't take away anything from the fact that each carmaker is essentially a business, and their main agenda is to sell cars, lots of them. This is the 21st century, and nobody's still selling cars that are going to last decades, like in the old days.

Second of all, and a hell of a lot more important, most modern cars have turbocharged engines, also mostly in the name of efficiency, and I hope you all know how hot a turbo can get under load. Older fellows might remember that in every turbocharged car's manual there was an addendum that urged drivers to keep their engines at idle for about a minute after some spirited driving, for the turbo to cool down.

Most newer turbocharged cars use ball bearing turbochargers that are both oil-cooled and water-cooled, so there is less heat soak, and the risk of oil coking is minimal following a hot shutdown of a turbo engine, but it still exists, though. I'm not entirely convinced that a start-stop system on a heavily turbocharged vehicle (think BMW M or Mercedes-AMG) is the best thing to keep it in perfect working order for years and years.

Last, but certainly not least, even if you don't a have a turbocharged ICE under the hood but your car does come with stop-start, there is still a durability problem. A regular engine will probably go through around 50,000 to 100,000 stop-start events in its entire lifetime. One that comes with a stop-start system will probably have almost a million stop-start cycles in the same period.

While an ICE is running, the crankshaft and most of the bearing surfaces don't touch, since they are separated by a very thin oil film, creating lubrication. When the engine stops is where most of the metal surfaces inside the engine actually begin to touch and continue to do so until the engine is restarted again. That small gap of time between engine “off” and engine “on” is when the highest friction takes place, increasing wear and tear immensely.

Is this amount wear and tear better to happen to your engine than those 5 to 10 percent of fuel economy you get in return from a “micro-hybrid”? That's not for me to answer, but I do know that I've turned off about 99% of all stop-start systems that I've encountered when test driving modern cars, and they weren't even mine.
 

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Unfounded fears!

For one thing a lot of new stuff doesn't use the starter motor! They start the engine by using a hybrid Alternator/starter, fire 'parked' cylinders, all sorts of clever stuff!

Electronics keep the water circulating to keep turbos etc cooled when the engine is stopped or don't stop the car when it's not within parameters. For a start when you are stressing the car a bit ( in S mode ) the start stop is off.

The systems are beefed up to take the extra wear and tear.

Actually if you look at it you only start a car on average 2 or 3 times a day. 20 years, averaging 3 starts a day is only 20000 starts. ( with a bit of time off for weekends, holidays etc ) Not a lot. My diesel truck starts and stops perhaps 20 times that when commuting ( i leave the s/s on ). It's done nearly 70000 miles in 3 years and there is NO sign of any wear on the starting components. I'm guessing in the 3 years it's started around 20000 times. When the vehicle has done twice it's mileage at around 150 000 it'll have perhaps 50000 starts on it but it'll have more to worry about than the starter!

:) :)
 

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Unfounded fears!

For one thing a lot of new stuff doesn't use the starter motor! They start the engine by using a hybrid Alternator/starter, fire 'parked' cylinders, all sorts of clever stuff!

Electronics keep the water circulating to keep turbos etc cooled when the engine is stopped or don't stop the car when it's not within parameters. For a start when you are stressing the car a bit ( in S mode ) the start stop is off.

The systems are beefed up to take the extra wear and tear.

Actually if you look at it you only start a car on average 2 or 3 times a day. 20 years, averaging 3 starts a day is only 20000 starts. ( with a bit of time off for weekends, holidays etc ) Not a lot. My diesel truck starts and stops perhaps 20 times that when commuting ( i leave the s/s on ). It's done nearly 70000 miles in 3 years and there is NO sign of any wear on the starting components. I'm guessing in the 3 years it's started around 20000 times. When the vehicle has done twice it's mileage at around 150 000 it'll have perhaps 50000 starts on it but it'll have more to worry about than the starter!

:) :)
If your under Warranty it dont come in to it but ........

The fact is wether its the Starter Motor or Hybrid Alternator and Battery etc

The replacement costs are all 2-6 plus times the price of say a basic 171 / 170 without start / stop tech .
and they WILL FAIL not for somone who has warranty or change the car every x years to worry about

It will be the person buying second hand that will go christ how much .
For the saving of a few pounds a year but when you do have a fault just a plug in diagnostic will out the fuel saving cost you saved in a year . >:D

and thats without cost of the expensive part and labour and coding on top .
 

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Discussion Starter #4
I hate the Start/Stop feature drives me bonkers so I just switched it off. If you go out car shopping put it on your shopping list to find a car that you can push a button/switch to turn it off.:wink::smile:
 

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I hate the Start/Stop feature drives me bonkers so I just switched it off. If you go out car shopping put it on your shopping list to find a car that you can push a button/switch to turn it off.:wink::smile:



Me too. I hate it and turn it off whenever I start my 2015 GLK. I only drive it about 2K miles a year and gas up about once a month, generally for under $20, so any savings it might provide would not be worth the aggravation. Still, since it's obviously implemented by the car's "onboard computer" I think it would have been nice if MB gave me the option of turning it off from the menu the same way I can turn off some of the other nonsense, like the equally annoying lane departure warning that causes the steering wheel to vibrate. You know stop/start isn't being done to save us money, only to allow car makers to show better MPG figures for "city" driving.
 

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I think this 'feature' as Paul Beretta (above) says, is to eke out those last few drops of fuel consumption for economy.
The problem being, perhaps, is when the start/stop relay fails? Another question (discussion point) is do you drive your car directly on a cold engine or let it warm up? I certainly don't, even tho' my fuel consumption reads tragic numbers for five minutes or so. Letting the engine oil get to it's or close to optimum temperature is worth the wait for a minor lapse in fuel consumption...
 

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I think this 'feature' as Paul Beretta (above) says, is to eke out those last few drops of fuel consumption for economy.
The problem being, perhaps, is when the start/stop relay fails? Another question (discussion point) is do you drive your car directly on a cold engine or let it warm up? I certainly don't, even tho' my fuel consumption reads tragic numbers for five minutes or so. Letting the engine oil get to it's or close to optimum temperature is worth the wait for a minor lapse in fuel consumption...

Agree on the issue of it being one more thing, or more likely a number of things, that can go wrong. Worst than some since it has the potential to leave you stranded in traffic.


As for warm up. While I can't speak for other makes, or even other Mercedes years and models, on my 2015 GLK350 start/stop only works when it's in gear and my foot is on the brake. I tend to just get in, start her up, and drive, but I'd imagine that most folks who sit warming up their engines do so in park.
 

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I think this 'feature' as Paul Beretta (above) says, is to eke out those last few drops of fuel consumption for economy.
The problem being, perhaps, is when the start/stop relay fails? Another question (discussion point) is do you drive your car directly on a cold engine or let it warm up? I certainly don't, even tho' my fuel consumption reads tragic numbers for five minutes or so. Letting the engine oil get to it's or close to optimum temperature is worth the wait for a minor lapse in fuel consumption...
No point in shooting off down the road with a warm engine and a freezing cold gearbox, bearings, U joints etc etc .

I was taught (47 years ago) to start the car, drive off and keep revs low until the car is up to running temperature. This is still the recommended process today The owners manual for my car says the same.

On top of this, I have an oil temperature gauge in the car and it takes 2x the distance (compared to engine/water temp) for the oil temperature to come out of the blue.
 
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