I can tell you for certain that it voids the warranty on any Deka/East Penn made battery. Considering the vast number of private labeled East Penn batteries sold into the marine market that probably adds up to 25-35% of the market this product would void warranty on including all the West Marine batteries... That is what one of the largest battery manufacturers in the US thinks about it...
Beyond that Fred Wehmeyer VP of Engineering at US Battery has physically tested the product long term in their batteries. They too will void warranty if that product is found to be in them. Fred said the guys from Thermoil have been there numerous times and the answer is still the same, no...
According to Fred the oil eventually breaks down into acetic acid, any organic compound added to the battery eventually will, and it attacks the positive plates. The oil can also attack the separators of some of their batteries.
I would suggest you have your US Battery dealer contact Fred to discuss "warranties" when he sells Thermoil to his customers...
Smells like snake oil, sounds like snake oil....must be snake oil......