C/D did an excellent piece on this a few years back. If anyone is nerdy enough to remember the issue, I will happily scan and post it from my print copy.
C/D described it as a "simple way to save fuel". And I agree.....Which is why I can't understand all the hate over this device...I wish my car had it.
The XC90 and the GTI of the poster above are both watercooled, both with electronic pumps to circulate coolant through the turbo after the car shuts off and that isn't even needed as coolant will flow around from hot to cold to hot on its own cooling the turbo.
While there have been issues with oil on some turbo cars in recentish years (early a4/passat 1.8t) that was mostly due to using regular oil and long intervals with too small of a sump, the NA engines of the same era had issues as well so the turbo was just the icing on the cake not the root of the problem.
There is really no reason to be worried about coking oil on a modern turbo car just due to start stop.
I'd venture to guess if the car is running that hard/hot that it also knows and is going to keep it on to help bring temps down, as in it would disable start stop on its own.
So my sort of issue with it is inline with your impression, likely others.
The oil temp of a modern car changes very very little from operating normally to idle. Water temp doesn't even change much in a modern car during normal driving. Plus you should be off the accelerations if not fully off the throttle for a several seconds as you properly noticed the intersection or redlight stoppage ahead.
The VW turbo Jetta hybrid will even shut off and disengaged clutch in a coast or sail mode. The BMW 3 series and I think 5 series will also shut down in a coast mode.
Here is the thing....This feature isn't for us. It's only to meet some arbitrary government number, a "cheat" if you will, in my mind, just like the TDI thing. Engineers met a number, and passed the wear and tear on components on to the consumer.
Starters, transmissions, oil coking, coolant temp creep in stop and go conditions (as the coolant isn't circulating in stop and go traffic), bigger batteries, the HVAC equipment getting different levels of voltage and load, wear and tear on the pulleys, bearings, and belts from constant stop/go.
All for the consumer to get a teeeeeeeny tiny benefit of mileage. But the manufacturer to get huge boosts in emissions testing. Because if the engine isn't running, it isn't emitting.
No on the coolant thing, first off they have electric circulating pumps, second coolant still flows without a pump.
Starters, while they still do fail, are pretty robust these days I can't even recall the last time I changed one.
I'm not entirely sure this is at all incorporated into the testing.All for the consumer to get a teeeeeeeny tiny benefit of mileage. But the manufacturer to get huge boosts in emissions testing. Because if the engine isn't running, it isn't emitting.
Don't care for it at all. At least in the C300 loaner we had recently you could disable it based on custom settings.
A couple who I know sold their $80k vehicle due to it randomly shutting off at stops, which no one could diagnose properly, irritating them to no end. Goes out and buys a pair of $80k vehicles which do it every time now, which they love and brag about every time it happens. I had to remind them that the manufacturers are essentially being forced to do things like this. In order to negate that idiocy, I'm going to go outside and let my unoccupied vehicle idle in my driveway for a couple hours. Then I'm going to dump a few gallons of old coolant out onto the ground behind my garage while I continue to work on burning my 10 cords of hardwood in my uncatalysed wood stove. mlm