I buy whatever's cheapest at the auto parts store. It's usually Quaker State 5W30 tho, with a Fram filter. Today i bought the deal at advance for 13.99, 5 quarts of quaker state and a purolater filter. I also bought some Engine Restorer and Lubricant to try out. We'll see how that goes even tho I've heard nothing but good things about it from friends.