I'm inclined to believe that the engine doesn't reach its sweet period until after 100,000 miles. Mine is at 132K miles and I think it's driving much better than when my dad gave it to me at 85K miles. I think these diesels only get better with age.

Alex

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1983 300D (parked for four years)
2012 VW Sportwagen TDI Manual
2001 Miata SE
1962 Chevrolet Corvair Rampside