i usally or i should say i have used synthetic oil since the seventies as iam getting to be an old man(65) i wonder if iam getting wiser or senile i change oil every 5000 miles. i live on the st lawrence river across fron ontario canada we do get weather that is below zero every winter.most old timers,older than me still use 10/30 and their cars start just fine.even when they buy new cars they use it they always laughed at me for using synthetic.the state of new york buy quite a few new cars and trucks and put two to three hundred thousand miles on them before they auction them off and guess what they use.amercian choice re refined oil in bulk tanks and all 10/30 new cars trucks tractors lawn mowers anything that uses oil they all get the same.that includes the state hospital predeters unit and the two prisons.conventional oil is close to sythentic mobile even says their super 5000 is good for five thousand miles.although the other oils dont say that i guess they are as a lot of the members here go that far on qsgb pyb vavoline and even st.thinking of going conventional after i use up my stash.so the question remains am i getting wiser or senile?