My (wife's) 300D gets about 20 or 21 in town, where it is driven most of the time, and around 24 on the highway last time I checked it.... I don't get to drive it much!
My 240D has been as high as 38, but that was two years ago on a long trip - all interstate, and no A/C running. The average is around 32, with half city/country and half highway driving.
76 240D - 550K miles
78 300D - 200K+ miles