Check to see if the car has ASR. Turn the key on and look for the amber ASR light. For some reason, it seems that the models with ASR have more problems with the ETA. It would be a good thing if your prospective car didn't have this option.

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1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles