Brother just gave me a 2001 Volvo with a turbo and 99,000 miles. I don't know when the last oil change was done. Before I changed the oil I added 5 oz of Seafoam to crankcase and ran the engine until warmed up. Couldn't get the drain plug loose (going back with1/2" drive) but did look at the dipstick. It was covered in bubbles about 1/64" in size. The oil shows no condensation sludge. After I added the Seafoam the occasional lifter tick went away and the engine ran smoothly and quietly. What could cause those bubbles? Was going to put in high mileage Mobile 1 and new filter.