The fuel economy on our 240D had dropped about 5mpg. There wasn't a noticeable change in power/acceleration. "Luckily", before I could begin my investigation under the hood, my wife got a flat tire one evening. When I jacked the car up to change the tire, I could barley turn the front passenger side wheel. I replaced both front calipers .... problem solved.

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1980 Mercedes 240D
1982 Mercedes 300SD
1985 Mercedes 300D
1993 Dodge Cummins Turbo Diesel