The 68 220D/8 noted below routinely got 28mpg over the whole 20 years that I drove it. This was a manual tranny and mostly in a rural metro area of ~30k pop. Lots of traffic lights and moderately low speed limits. On the highway it delivered 30 to 33mpg at 60 to 65mph. Must remember that most of the years were in the double nickel era. Had one part tank of 45mpg between Amarillo and Lubbock Texas, greatly helped by a tremendous north wind. Wish I had a brand new one sitting in the driveway!!

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150