o,donnels medium/hot work a treat in that engine dude,,,if you speak to the chap from rc direct who supply them engines he will tell you the mcoys mc9 dont perform to well in them ,,,yes i have tried 1 and yes he is right as it never ran to well so i put my trusty o,donnels in and no problems at all ...runs like a dream,,,he did recomend the rb6 or 7 though and i will get some to try