The only additive we suggest to our customers in our shop is Power Service products. After a lengthy telecom with a 'salesman' about their product, we first used them in our own vehicles with very good success. I put 'salesmen' in quotes because this gentleman was more than a salesman, he wore two hats, he was also in product engineering. This guy knew his stuff. I do not like to a salesman who knows less than I do about their own product which seems to be a trend in marketing today. This company also has the contract with Walmart for fuel storage and fuel system integrity related to fuel. Keeping in mind the size of the Walmart fleet, this speaks highly about this company and its products.
They have one of the few products that can clean up gelled fuels, which can happen in your unprotected system. The two products we use consistently are Diesel Kleen (above 30F) silver bottle, Diesel Fuel supplement (below 30F) white bottle. It is available every where. New engine warranty will not be affected by this product.
Lewster had a post about his success with this product. I have numerous customer plus out own vehicles which will serve as examples of how well this product works.