I meant do a search and see what forum members say they're getting. For example, this neat thread on 190D mpg. Interesting to see how automatic vs manual makes a big difference...

You could also compare what members are saying about 300SDL vs 300D mileage. I didn't actually look this time but my hunch is they're the same, the weight difference isn't very big (only the 190 is significantly lighter). They do use the exact same gearing btw.