I have a 1993 190E 2.6 with 65,000 miles on it. I average about 24 miles per gallon per tank. About 22 for pure city driving, about 26 for highway.
I have never, under any driving conditions gotten worse than 20 miles to a gallon. Keep in mind, that includes driving in 100+ degree temperatures (Dallas) with the AC on high most of the time. I am very happy with the gas mileage.