Well it is summer here in Missouri, and we have high humidity and temps. I buy my fuel at a truck stop that sells a lot of diesel. But I was just wondering if I should add a bottle of biocide to be on the safe side? I never let my tank get below 1/2 full and run through around 20 gallons a week. Do I really need to add this stuff or just keep using my regular fuel additive to keep the injectors clean?