Valve job and chain every 200,000 miles or so, and if the older cast iron engines are any indication, if you don't overheat it the bottom end will go at LEAST 500,000 without work, then only needing rings. The siliconized aluminum block should wear at about 1/5 the rate of the cast iron, so you are looking at 2.5 million miles before the cylinder walls wear out!

Should last indefinitely, I've never heard of one wearing out that wasn't badly mistreated (severe overheating being the worst possible thing to do to it).

Use synthetic oil and you may even lengthen the time between valve jobs!

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!