I got about 30 in the W115 with auto tranny. Never really measured it, as it usually broke down between fillups!

Check the timing chain for stretch if you have low milage --- late injection timing will reduce both performance and milage badly. So will dragging brakes from sticky calipers (meaning it's probably time for rebuilds on the calipers).

Wonderful cars if not rusted away or abused!

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!