My '95 E420 gets 25 to 27 on highway - cruising at 70-75 mph; running the AC drops the mileage to around 25 mpg on the highway. It loves the highwat.
City is 14 to 17 depending if is just a bunch of short trips (my daily commute to work is 3 miles), so that mileage is really bad. If I'm running an errands and doing more suburban driving, then it's around 16 MPG.
Overall, the car does 18 MPG. Not bad mileage, but the engine requires super unleaded which can add up.