Getting back to the original question: outside of non-engine related things like tracking down a phantom slow coolant leak my engine with 209,000 miles has no other engine noise than what's suppose to be heard and burns or leaks very minor amounts of oil. It is a very strong engine. I change the oil a lot too, by color as well as mileage. If I don't like the color of it - it's changed.
1994 E320 Wagon (Died @ 308,669 miles)
1995 E300 Diesel (194,000)
1999 E300 Turbodiesel (244,000 miles, dies at 255,000)
2006 Toyota Tundra SR5 AC 4X4 (115,000 miles)
2011 Audi A4 Avant (129,000 miles) hate this car!
BMW 330 xi 6 speed manual (100,034 miles)