vjjack04
Junior Member
Ramsare4real, I had Shell Rotella synthetic, now I have Mobil 1 Delvac full synthetic 5W-40. Just seems to me that there must be something very particular concerning the 15w-40 oil problem it has all the API rating and other qualifications. Would seem that as soon as the truck is at operating temp, the oil operating range would all be evened out, so to speak.