I mixed 3 different oils in my Diesel 5w40 Synthetic Oil In 6.7 Cummins
) Check out our new spot to find ALL our TFLstudios content, from news to videos and our podcasts! Basic answer is 5w40 year round is fine on a 6.7 Cummins. Since a once a year or every 15000 miles is now the recommended service interval, just use the 5w40. We use these trucks in a hot shot trucking company. They get used exclusively for pulling gooseneck trailers 36-40ft. Avg gross ...