Four years ago I bought my '84 300CD on Ebay from an Erie Penn. dealer & drove it to central Florida. Took it easy because I didn't know the condition of all the fluids. Car had over 270,000 miles on it at the time & needed some valve work. Got 31-33 mpg at 60-65 mph. These cars need an extra gear at highway speed. I would imagine high 20's over 75 mph. Paul.