weight AND idleing make a big difference. My commute to work is 3/4 rural and 1/4 in town with a couple red lights and stop signs. My 300M has the instantaneous and trip MPG computer. On the rural part of my ride I can get 30 MPG driving gently, but add 2 or 3 traffic signals to the mix and the overall MPG drops to 24. Put another way, for each traffic light, you have to drive 5 or 10 miles open road for your MPG to recover. At short traffic lights, (with an auto), shift to neutral, this mocks a stick shift. RPM's will pick up slightly, but the engine vacumn picks up also because the engine is not laboring against the torque convertor. For long lights, kill the engine and restart.