“You can also find comments from engine re-builders who can tell if an engine was lugged by looking at the rod bearings.”
The engine rebuilders are making an assumption. Unless they know the driver and have gone riding with them, they really can’t tell. But I was not talking about lugging an engine, I was talking about loading. The point at which an engine is lugging is based mostly on the cam profile. Many engines operate smoothly under heavy load and low RPM.
Now I have had vehicles that I would not operate under heavy load at 1800 rem or less because they weren’t designed for it. They will lug badly, but I have found many engines are perfectly happy at full throttle at 1800 rpm or less.
“do a little searching for ‘hydrodynamic lubrication’ and you’ll find that low speeds and heavy loads do a double whammy on sleeve bearings.”
You are also making an assumption that I don’t know anything about “hydrodynamic lubrication”.