The 2.5 is the om602 and is considered a modern replacement to the om617 that your old 300d had. Yes it is just as reliable/durable. And YES w124's have mono wipers. And YES the w124 is a nicer car than the w123. Go find one you like, drive it, and buy it. And YES babymog knows w124's like the back of his hand. Listen to EVERYTHING he says. YES

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08 R320 CDI current

Past
95 E420
87 300D Turbo 5spd
90 300TE
83 300SD
85 300TD
92 400E
85 190D