That mileage sounds about right for us too...yes, they are much heavier than a coupe or sedan...darn thing has lead weights in it for solidity ! On my new title it say the car is close to 3900 lbs, more than my 500E...but I have conflicting info on their actual weight. Bottom line....they're heavy. I think the only way to get close to good gas mileage is to put the cruise on at 55 mph.
Mine is a very late 1995...was built in December and apparently delivered here in the states in 1996 but it sold as a 1995 model.