So a guy in a facebook group about Ford Capris i'm in is building a Turbo engine for the street , he posted a question in the group asking if it's a must to use a full synthetic , this has sparked a big convefsation and people have suggested that he should use M1 15w50 full syn , and others have suggested what most of us run which is Valvoline Vr1 20w50 conventional, so is it a must to use synthetics in a turbo engine or does the turbo completely destroy conventional oils? He's running an oil cooler too and about 12 psi of boost on a blow through carb setup