Make sure you are running the test right.

You've got to have level ground and no wind. You launch the car by selecting the lowest gear and using both feet to load up the drivetrain, then release the brake slowly. Even in the 190D you might be able to get a little bit of wheelspin and keep it from bogging on the launch.

Also make sure you are using a stopwatch - best to have someone else doing the timing.

Finally, make sure all the accessories (A/C, lights, etc) are off for the test.

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1983 240D automatic, Orient Red, 174K
1983 240D manual, Biscayne Blue, sold at 341K