synthetic blend or a full synthetic 5w-30 is what most call for you will be safe with a 10w-30 either way the two numbers mean the thickness of the oil when the engine is hot and cold the w stands for weight meaning 10 weight to 30 weight oilAnswerI use full synthetic Mobil 1 10w-30. and I've got over 200,000 on the odo.Might try royal purple though. If you've got a double overhead cam only put in 4 qaurts no more. it stops the oil from being whipped into a foam by the crankshaft. and if any of that makes it to the cam bearings they're toast. The single overhead motors don't have this problem with the cams but I do it anyway helps with oil life.