Flushing has its place
Wow. I will no doubt change my thoughts about flushing but I feel there still is a place for it. I just bought a 1983 300SD Turbo Diesel and have no idea how well the the engine was cared for. A flush that drops lumps or thick sections would require further investigation. I ordered lower oil pan and valve cover seals just in case I have to clean slug from the bottom of the pan. Yes if I owned the car forever or knew its history a flush may not be that beneficial. For a new used car, I have to go with it.
Separately I read in the manual that up to a quart of oil can be held up during an oil drain. Don't like that. I'm thinking it could be the oil cooler lines. The oil change procedure did not look like it would drain that section. Anyway I have started spraying penitrating oil on the hose fittings.
In surfing the manual I noticed oil spray nozzles pointing up to the pistons. So how often should those be checked? This could be a place a flush could help. Any buildup around the nozzle would hurt the spray pattern. The book said pluggage of a nozzle can ruin the engine but gave no info on when to check.
Anyway, I may not flush all the time but never or not after acquiring a new used vehicle, naw I'll still do it now and then.