unless you drive in the artic or the dessert or own a money printing press,use regular motor oil(i only use valvoline or castrol).latest thinking is semi-synthetic which give you the best of both worlds.remember,most of the engine wear occurs in the first few seconds when the oil starts to circulate so for a very short period of time you have metal to metal contact unless you believe in teflon-coatings.5w30 will help pump quicker also.