My car has 18,000 miles and I have never drag raced but once in a while I like to step on it and feel its power. Since I bought the car I have changed the oil at the dealer every 2500 - 3000 miles with their semi-synthetic oil but I want to start using my favorite oil which I used in my bimmers, Red Line Synthetic. Since I live in Miami, my question is, should I use 5W20 or 5W30.