Guys I have a 2005 Toyota Tundra 4.7 L motor with 5,000 miles on it. Live in NC . I have ran Havoline 5w 30 dino in it to date. Did the only oil change at 1,000 K's. I change the oil just once a year with the amount of miles I put on it. LOw amount . I use it for trips and exploreing really. I want to switch to synthetic. Wallyworld has Mobile 1, Penzoil Platnium and Castrol syntec (spelling ,sorry ) . Im no oil geek so all these post about the different groups makes my head spin. Out of the 3 ea mentioned and cost not being an issue out of the three, which would the the choice. I know that is an loaded question for this site ..LOL.... I know the Havoline has been good oil and all but a friend of mine just had issues with his Toyota camry 4 banger with about 60 K's on it and we pulled the valve cover and it was sludged up bad. He claimed to have changed the oil very 5000K's. So while I know the partcular engine has had this sort of problem from Yota, I was wanting to step up and give my nice Tundra a better oil for protction ( in therory ) and go with synthetic oil. Thanks in advance, WarDawg