Larry - You are ABSOLUTELY right..change the
oil when it's HOT. All the sludge/junk washes out. My MB car is a low mileage vehicle; however, I have an old Toyota truck and an Accord that collectively have about 550,000 mi. on them. When I pull the valve covers off, you'd swear you were looking at a new head - no sludge - no cam galling - nothing that resembles wear or the kind of mileage I've logged.
Too bad so many folks don't realize that changing the oil when it's hot can add a TON of miles to the life of an engine.