Only flown one glow engine, OS40LA currently in an ARC Ready 2 Trainer. Previous trainer speared into the ground from a great height and we had to dig the engine out of the crater. Hosed it down and fitted into the Ready, it's been doing its thing for 3 years. Better on 11" props than 10" in my experience, but having said that, when you're only doing left and and right hand circuits (and the odd figure of eight when the wind ain't blowing) it doesn't make that much difference. So, I like it. Others in the flying club quite like ASP four strokes, quiet and inexpensive. On that subject my OS40LA only cost £50...

The worst engine I ever owned is in the front of my wife's 1993 Mini. It had a cracked cylinder head that took AGES to diagnose.