My '83 300SD has 185,000 miles and gets 20 mpg. (I just recently purchased the car). When I reviewed the repair bills from the original owner, there was a note that the mileage dropped to 20 mpg after the 45,000 mile service (coincidence, probably), but that's when it was first mentioned. Later trips to the shop were for checks for fuel leaks, etc...none found. The car has been very well maintained and fuel filters etc replaced as required. Why would this car get such low mileage? My '82 240D gets at least 30 mpg and it now has 350,000 miles on the engine.