my friends friend quarter mile bracket car with a 350 chevy uses castrol 10-40 high mile type oil . that one has alot of lumpiness when idling and no problems with engine or camshaft. one other guy has a 1300 suzuki with some other hipo camshafts and valve springs named webcams and he has used qstate 10-40 for over 40 thousand miles of street riding since 2001 . thats 40 thousand miles and still running good !!!