i say Pete wit a Cat C-15 all the way...i kno some1 who ordered a brand new KW wit a Detroit and now cant get the truck started...brand spankin new...!!!
i use the Amsoil 5w-40 oil and thier oil filter...i change my oil every 10k and oil filter 5k in between...wanna keep the engine juice kleen and the turbo alive and spinnin !!!