50 degrees! WHAT LUXURY! I live in northern Alberta, Canada and we have been know to fly at -40 degrees. We did it on a New Year's day just to say we were the first to fly that year. I don't recommend flying at -40 though. It's really brutal. We do fly often at below zero temperatures with skis on the aircraft. I usuually keep the plane in the warm vehicle until I am ready to fly then quickly start it up. Some fliers put the engine under the car exhaust for a few minutes if it is really cold. I don't put any special additives in the fuel though. I just try to have a well broken-in engine and have it adjusted properly.