I have used both Mobil one synthetic and Now Amsoil synthetic with no adverse affects and I use 100LL all the time, no auto fuel.
No sludge build up. Oil stays clean for a long time after I change it. I change oil every 50 hours.
I use 10w-30 synthetic.
There is no way I would use anything other than synthetic with a turbo charged engine because synthetic oils can handle much higher temperatures.
New Ulm, MN 56073
261 hours and counting