Lets trsde! My 87 300e (71,000 miles) once got 22 mpg as it's personal best on a run to SF at 70 mph. I seem to get around 19-20 overall combined freeway and city. I wouldn't mind your mileage at all.
After all, this is 3 liters geared more for performance than economy, and pulling close to 3500 pounds around! I guess trading for a later w124 E320 with the m104 engine, or trading for the diesel, would get you better mileage. Alternatively, switching to Michelin Energy tires might up the mpg up by 3-5%, but the trade off would be performance and handling.
I like the performance, and am willing to sacrifice a little comfort, mpg, and tire life for handling. Have a great Holiday!!
2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)
Click to see 87 300E