I definately think the NAV system and it's extra Fuel Economy (I hate to call it "Consumption")/Energy screens make a big difference for me. As others have said, I play a game with myself and try to get better mileage every trip, and every tank. Being able to see the energy screen graphics is a big help in learning how this fantastic technology can best be used for the best gains, and the "best" and current trip resetable indicators and bar graph are added tools.