I bought my 93 300D as a daily driver for $6K. So far I have spent about $700 in parts (2 tires included) doing pm type stuff. Probably another $500 or $600 and it will be up to date.

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1993 W124 300D 2.5L Turbo, OM602.962
2000 Chevrolet Cavalier, 2.4L DOHC
2002 Ford Explorer, 4.0L SOHC
2005 Toyota Prius, 1.5L

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