Don't veer away from an om602. Head gaskets aren't that much of a problem as people say. They go bad, but they go bad on every car at a certain point. Vacuum pumps go bad too with age, that's pretty normal too. They aren't fast but will cruise at 70mph and get mid 30s mpg all day long. You won't notice much of a difference between the om603 and om602 powerwise

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Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k