I am switching from Delo 15w40 to Amsoil 15w40 in a gas engine with 40,000 miles. I do not want to do a 'solvent' flush, and am not worried about the engine being 'gunked up'...but, is there any OTC product that can work as a neutralizer for the old oil? Just to run for a while before I change over...Rislone? MMO? CD2 detergent?