Hello, I have an 2004 ford exp 5.4 2v that calls for 5w20 oil, the problem i live in florida and tow a 5000 lb boat. I have tried many different combos of oil and filters, I have noticed with valvoline 5w30 conv oil this engine sounds the best. I have one of those engines that have piston slap, which of course the dealer says it's normal. Just wondering how many people are using something else than the recommened oil weight. Thanks for all your replies, great site.