The major oil suppliers have spent a ton of money researching and testing various formulas for their HD gas and diesel service crankcase products. Care is taken to balance the additive package to the particular base oil, so performance can be predictable. To just dump in additives or supplements at will, is probably undoing a product that would have been better left as is. Delo 400 is factory fill at Peterbilt and Kenworth, it would be pointless to try and improve that situation with a magic formula supplement.