It is actually the bore (cylinder walls) that "Glaze up", in most cases it is caused by the piston rings not making firm enough contact with the bore. Compressed air and fuel go down the piston to the rings and in behind the rings and force them against the bore. So when an engine is idling and not much pressure being produced the rings are not being pushed into the bores as hard and this causes the bore to glaze up. When you run an engine "in" you are told not to hold constant speeds for long periods, as this same effect happens, you should work your engine to get the rings to conform to bore shape and bed in. Also Synthetic oils can cause glazing when running in a new engine, Mineral oil is the go for the first few oil changes. My BA GT ran Synthetic oil from new and was using more oil than it should, FPV engineers recommended Mineral oil and drive it like I'd stolen it, after another 5K it was run in. I have had diesel trucks and I only ever let them idle long enough to cool down and the turbo to spool down and cool, Regards Frank.