[JohnAG]

I'm just curious if I'm the only one who is somewhat concerned with the wear and tear to the starter motor and battery of the auto start/stop function, that I'm seriously considering leaving it off all the time. I don't know how much improvements have been made over the years to the starter motor design and parts, but electric motors in general have a limited service life due primarily to damage inflicted by friction and heat. Again, being a former mechanic, I've replaced many starter motors, and with this function a 1 hour trip through a busy city route could probably log on 1 years worth of wear and tear compared to cars that don't have this function.

Again, I don't know what improvements have been made on the bearings and the innards of the motor itself, but unless it is rated to last for 1 million start and stop cycle, I'd feel weary in having it on thinking that it will die on me the day after my warranty expires.

Same concern goes to the battery since all the electrical devices remains on when the engine cuts off. Has anyone experienced pre-mature battery replacement (around 1 year or less)?

[Peter_R]

I am sure you will find that BMW have carried out considerable testing on the starter motor components and they have been designed accordingly and will last long enough.

Again in my view there should be no problem with the battery lasting just as long as if there was no start stop system in the car. Again I would have thought that BMW would have tested this scenario.

I am from the UK and never have a problem with the battery all though I did when I first took delivery (1 year old) with the car telling me the battery voltage was low. I purchased a CTEK MXS 5.0 charger, and charged it overnight for several nights and all has been fine since.

[Tjalle]

Instead of - typically - 1bhp of starter you now have 4bhp, and as Peter said - it will laaast.... Both Bosch and BMW has done extensive tests.

I will, however, if driving in "high stop areas" go to Sport mode, both to "take no chances", but also for comfort and convenience (temperature).

I top up the battery once a month with my Ctek. Cost for the battery for a BMW is outrageous compared to my SAAB.

[The X Men]

The battery in your BMW is a AGM battery, which has a deeper cycle than a regular battery. Lets face it, these modern day BMW are battery hogs, they do have some electrical charging and drain issues, but it is not due to the auto start stop system.

[ianfp]

Extra mechanical wear on the starter motor and drive mechanism has been reported. I only use 'start-stop' under certain conditions and where I know I will be stationary in traffic for more than a minute or so.

[JohnAG]

It sounds like this system can't be a fire and forget type system. The fuel saved on a less than 30 second stop is probably worth less than the wear and tear the system is putting into the starter and battery.

Any battery issue can be associated with the system since the battery is fully maxed out when the engine is off and the AC, radio, GPS, lights, etc. are on. And as any battery in existence is charged and discharged, this shortens their service life.

[Ranger 6]

I've got two turbos. My concern is that as soon as the oil stops flowing it starts baking in the heat. I don't want clogged oil ways or any knock on problems.

Batteries and starters have been covered.

[JohnAG]

Originally Posted by Ranger 6

I've got two turbos. My concern is that as soon as the oil stops flowing it starts baking in the heat. I don't want clogged oil ways or any knock on problems.

Batteries and starters have been covered.

That's a good point. I wonder if the oil temp is taken into the algorithm which shuts the engine off?

[Peter_R]

Originally Posted by Ranger 6

I've got two turbos. My concern is that as soon as the oil stops flowing it starts baking in the heat. I don't want clogged oil ways or any knock on problems.

Batteries and starters have been covered.

You won't have a problem.

If the oil temperature (as it leaves the turbocharger bearing cartridge) is hot enough that the oil might “coke,” or have carbon particulates drop out, the stop-start won’t activate.

[Ranger 6]

You have a good knowledge of these things, but really? Have they been diligent enough to have sensors and that criteria built into the system logic?

Happy to be corrected

[Peter_R]

Originally Posted by Ranger 6

I've got two turbos. My concern is that as soon as the oil stops flowing it starts baking in the heat. I don't want clogged oil ways or any knock on problems.

Originally Posted by Peter_R

You won't have a problem.

If the oil temperature (as it leaves the turbocharger bearing cartridge) is hot enough that the oil might “coke,” or have carbon particulates drop out, the stop-start won’t activate.

Originally Posted by Ranger 6

You have a good knowledge of these things, but really? Have they been diligent enough to have sensors and that criteria built into the system logic?

Happy to be corrected

OK, you are happy to be corrected. Your words, so please read on because that is the reason I will follow this up. No other reason.

I was an aircraft engineer followed by an IT engineer allied to aircraft systems and I researched this problem exactly on the web some time ago (3 years) when I purchased the newly released F31 320d Sport. I quoted from a web site after checking again. The wording I stated was word for word from another manufacturer's website and repeated as follows:

Originally Posted by Peter_R

If the oil temperature (as it leaves the turbocharger bearing cartridge) is hot enough that the oil might “coke,” or have carbon particulates drop out, the stop-start won’t activate.

Just remember when a new technology is created it is not just kept as a jealously guarded secret, it is patented and used throughout the world. It makes companies large profits. That is how industry moves on and companies grow. Many of these new technologies are created by ancillary component companies such as Lucas or Bosch and put into production in many manufacturer's vehicles. You only have to look at the ZF 8HP transmission made by Friedrichshafen's subsiduary and used in BMWs. If you look at the site below you will see which others use the same basic transmission.

https://en.wikipedia.org/wiki/ZF_8HP_transmission

Now I ask you a question. Not being facetious mind you...Do you not think that given the amount of vehicles that exist in the world that the problem of oil carbonisation inside turbochargers has not been thought of and addressed?

Additionally as well as being an aircraft engineer, one of my jobs in the 50 years was that I was in charge of the Royal Air Force Spectrometric Oil Analysis Programme at Woolwich, where we checked all oils used in military/ civilian aircraft and military vehicles for the effects of heating and carbonisation.

PS. I never post hearsay. I research absolutely everything before posting.