Time and time again I have heard the argument that one shouldn't let diesels run on low load or the bores will become glazed and/or the rings stuck. At one extreme, there is running the engine on tickover, in neutral, for hours on end to generate electricity and heat water. But there are times when we want to motorsail with only a very low power. Looking at my engine and speed curves, I would get excellent economy at about 25% of max rated power and I can also see that I might like to motorsail at 10% of rated output - but is it safe to do that? At what output level can one feel completely comfortable about letting the engine run 24/24 - 10%?, 20%?,.....80%?