We get 25 mpg with a 70/30 mix of highway/city, and that's all rush hour driving. I've seen close to 30mpg on long highway trips where I kept the cruise control pegged at 110 km/h (about 68 mph). And that's with a 4Matic wagon too. The only repair I've had to deal with is replacing the accumulators for the rear air suspension at about 105K miles but I do know that the original owner had the transfer case replaced under warranty at about 30K miles (service records indicate it was done but don't give a reason why) and also had a mass airflow sensor replaced, common with all kinds of MBs.

__________________
Jonathan

2011 Mazda2
2000 E320 4Matic Wagon
1994 C280 (retired)