geeter,<div></div><div> I have used AMSOIL Dextron ATF for after run oil in my YS engines with very good results.</div><div>If you can find a synthetic air tool oil and mix about 25% total content with the ATF that will work well.</div><div>The reason you do not want to get any petroleum in the engine is it will kill the diaphragm.</div><div></div><div>That being said, most the people I know with YS four stroke engines don't bother with after run oil.</div><div></div><div>Happy flyin', Oscar</div>