I run Chevron 5w-40 full synthetic in mine. We buy a 55 gallon drum and run it in everything from our dmax's, gas, small engines, and tractors. Never had a problem with it. Always run oem or wix filters on everything too. I'm not sure about back east, but was told by a Chevron engineer that the Richmond plant in California makes all the base oil for everyone on the west coast, Chevron is the cheapest though because they don't advertise like mobil one or castrol or the others do. We recently switched to all chevron grease as well because it was cheaper for the same thing we had been getting. Just my opinion though.