You can use any of the additives listed in the fuel additive study thread or you can go as simple as using some TC W3 Two Stroke oil ( 1 ounce of oil per every 2 gals of fuel in your tank )Hello all. I have 1998 Chevy K3500 with the 6.5 TD. I am new to these engines. Is there something i should be adding to the fuel every time i fill up this diesel? Want to make sure I’m doing this correctly. Any advice would be much appreciated. Thank you!