I've just had my M5 tuned up. The valves were adjusted, the MAF setting returned to factory spec (apparently a previous owner had set it to run lean), the cylinders (airflow) balanced and the spark plugs, rotor and distributor renewed. (You should have seen the rotor! It was a mess.) The engine runs much more smoothly now and I anticipate more power and better fuel economy.

Before all of this, I was getting 16-18 MPG around town and ~23 MPG on the highway. For comparison, would some of you mind telling me what your average MPG has been? Thanks!