crewstx...your'e in luck:
because in your back yard,Dickinson Tx. is a facility that has been blending additives for many years. He started in the aviation industry because no-one else was doing it...that is blending additives for aircraft engines. And his products are among a select few that actually work. He claims a gain of up to 10% gains in fuel miles for diesel and gas...this I've confirmed with my own usage.
To understand the additive market you have to know that the products your'e buying off of the shelf are not manufactured by but blended, packaged and sold by such as Lucas, Amalie and so on. The people who manufacture the most are Lubrizol and then Exxon/Mobil, even Shell/Texaco doesn't manufacture their own additives, they buy them from Lubrizol.
With this in mind each who buys their base products blends differently...and of course with profit margins dictating quality.
The product mentioned earlier...and for this I've tested many and the only one that I've gotten and appreciable gains from are:
Am/Fleet Powerlene for gas engines
Am/Fleet Megatane for diesel engines.
I buy mine at Standard Auto Parts stores in the Houston area.