steel said:Rotella all the way if u want to save money. We run about 17 trucks out of my shop and mostly 5.9 cummins and a few 5.4 gas motors. At the shop its amsoil the whole time. 300,000 plus out of the gas motors at 7,000 oil changes. I run ansoil in my personal truck and royal purple oil in my wifes car and all small engines. We run marine 15w-40 marine amsoil in all my equipment. I have close to 20,000 hours on 2 perkins motors and they hold good compression. I m a maintance junky though but, i cant afford the break downs in the field because we didnt service equipment.