Martin, I have 4 sons who bore holes in the sky with hi-powered glo engines. Too fast for my old eyes and reflexes. I'm about 10 ft behind the planes. They give me a queer look when I start playing with my diesels. (Poor Dad, he's lost the plot). But guess who supplies all the glo fuel, plugs, etc. How's that for father/sons involvement. QUESTION. With 40/45/91 diesel engines (new), the use of muffler pressure. Yeah or nay? Exhaust gunk into the tank. Have read a lot of conflicting reports on this subject. Am using 15% Coolpower (synthetic) and 5% Castor. All converted Glo engines, and I have reduced the carby throat sizes. Your thoughts, please. Glen