i highly doubt the mobil 1 oil is the problem? what oil weight were they using that the cam was heavily worn? i personally use mobil 1 synthetic 15/50 with a mobil 1 filter.. and ive switched over to penzoil for a bit to see if i can notice any difference..and on pen i run 15/40 still with the mobil 1 filter.. i have never had a problem? the mobil 1 filters are also high volume..what filters were they using? what spring pressure? how where the engine bearings? honestly everyone here know's there are a lot of factors that could cause problems i wouldn't blame the oil?