I use it, buy it in larger quanities and save $$. I use Rotella DFA get it at Sam's Club 4-96 oz bottles for $33. 00 plus if you go to Rotella web sight you can get a rebate request form for $8. 00, so it ends up costing $25. 00 or . 02 cents per treated gallon. It does what they all claim to do, keep fuel from freezing, cleans injectors etc. etc. You can also buy Power Service, which several members use, and their are several other brands. Now the question about if you need it??? Thats up to you. Cummins says that you don't need it and just use winterized fuel during the cold months.