I use Brakekleen regularly on model engines and have not had any o ring or gasket problems. Since the product is designed to be used on brake systems, which contain seals, gaskets, and o rings that are likely made of the same materials used in model engines, I'd be surprised if there was an issue. Anything that can stand up to nitormethane, alcohol, and burning oils in RC fuels is, IMO, unlikely to be damaged by Brakekleen