^^^^ The endless debate that never ends.... or gets answered - LOL
The best answer..... is to use synthetic, and change it regularly..... and more often if you drive it hard.
I'd also recommend staying with the SAME sythetic oil for the life of the car.
Is any particular "brand" of synthetic really going to nake a difference? I doubt it.
I use Mobil 1 as well..... I trust it/.... so do a lot of guys. 44k miles with a turbo upgrade, and it doesn't burn a drop.
Penzoil synthetic? Sure, why not......