Oops I didn't think about this when writing the original post but apparently it's 97,4 UK Gallons per mile.. that's "only" 81 US mpg! Edited post title to reflect this..

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Tomas, Sweden
1966 Mercedes Benz 230S with OM617.912, automatic. Disk brakes from W108
1983 Mercedes Benz 300TD grey, OM617.912 and 5-speed manual
1983 Mercedes Benz 300TD blue 7-seater, OM617.912 and 5-speed manual