Not trying to be negative on Amsoil products, I think highly of them, and used thier trans fluid in my last truck, but what would happen if you needed waranty work and the dealer found out you only change oil every 25K? Just sayin. I haven't got to the first oil change in mine yet, but in my previous truck I used Mobile1 and changed every 5K. It had 152,000 miles on it when I traded it in and still ran strong. I'm leaning toward using Motorcraft Synblend with the Motorcraft filter in mine.