I always used mobil 1 (synthetic oil ) in all of my cars, one of them, my Saturn sc1, always well maintained,
I discover a clicking rattling noise on the engine, I google it, since I always take care of the car, (other that the engine given up) I read on more than one website the same issue with mobil 1.......
I change it to castrol and the noise stop, no more noise,
I always thought mobil 1 was the best oil,
so, now I use castrol on all my cars, ( synthetic oil )
keep in mind I'm in austin Texas, we have 100 degrees temperatures pretty much all the time