I have used Mobil 1 for some time now, and no problem at all.

One of my trucks got 400K on the engine, and I'm rebuelding it now. Take it appart and no issues on the cleaning parts (no mudge, no gel like oil or nothing like that)

Also use Penzoil Synth on the rear end. No place here sells Synth fot tranny.

On the performace side, I just cant messure it, but I'm sure it helps a lot. My personal experience with my 69 SS Camaro was a drop of 40 degrees on Oil temp. That means less friction, with translates in more power.