I run Rotella T5 Diesel Oil 10-30. Mobil 1 is probably one of the worst oils for us old Tappet style rocker people (B series, D series, H series) since the EPA has ordered oil companies to remove most of the zinc content from their products. This is because Zinc is not emissions friendly and now with roller rocker technology is no longer needed. This puts us people out because we start to have rocker pad and cam wear.