Change your oil when it needs changing and any decent synthetic will do.
I have gotten 300,000 miles with dino Castrol 20W50 and 3000 mile oil changes. Todays engines have better surface finish, less friction, better materials etc...
I would tell your friend that he should either drop the oil harassment or buy you the oil of his choice and give it too you free of charge! LOL
Your water pump,alternator,transmission,wheel bearing, sheet metal will all fail long before your piston rings, and cam lobes wear oil due to the oils make up.
Filtration, Clean Oil, Fuel Control those are far more important then oil make up in most modern applications.