my 5spd manual 190e2.6 gets about 20mpg in the city and about 26-28mpg on the highway. For daily driving on the highway, i usually drive around 80mph, with the engine at 3000rpm, in fifth gear. For out-of-town driving however, where i get the chance to probe the car's limits (and mine), the mileage i get will not be ideal, but what's a few dollars' worth of gas compared with the adrenaline rush (scanning for cops, that is)?
Like the other guys, i have also been religiously keeping records on odometer-fuel fillup data, and that's how i can back up my claim on city and highway driving mileage (kilomete-age to us canucks). I also keep records on oil consumption, logging odometer readings with the amount of oil added, to be sure i am within the "normal" consumption level quoted by benz.
and the trip meter reading before i reset it at every fillup gives me an idea of how i fared for the last fillup.
the 190e has a drag coefficient of 0.33, which is high by modern standards. At least the 190e has a smaller frontal area than the W124, which makes it generate less drag. Still, from the aerodynamic wind roar it produces at speed, you can appreciate where all the power (and gasoline) is going.