I did not read about that before:
2 weeks ago I tried a cheapo gas station.
Car ran like crap.
Poor acceleration. Poor idle.
Hard shifting (tranny made some clunk..)
Really scary was
engine leaked oil, probably at the rear seal.
That means bad gas causes excessive crankcase pressure.
Now I switched back to my usual ultramar 87 octane
and the leak is gone.
At least the driveway is dry now since 3 days.
car runs smooth and shifts smooth too.
If it starts leaking again I'll write another post here and start crying.