I have been using Castrol Syntec 5w30 ever since I put my motor in. I think I will start to put 10w30 like i did before the swap. 10w30 worked fine all year round here in Oklahoma. I noticed that the 6 cylinder would have a faint ticking sound with the 5w30 so i want to give it a little more weight. oh and temperatures here range b/w 2 degrees winter and 115 degrees summer worst case. but usually winters are in the low teens and summer around 105. __________________ |