You don't think they are going to use a product that may give them an edge weather real or perceived even its not made by their sponsor? Thats what he saying in the video, Valvoline was not cutting it so they used Amsoil and that was kept secret. So what? Apparently Valvoline never knew or maybe did not care as long as it was not made public , he won and everyone thought Valvoline was the reason.
I very much doubt they had a chemist on the scene testing to see if his oil was Valvoline.