i've pulled 39mpg on a 4 door with D16. In the city, i always lightly accelerate and shift at 2000 RPM when its not going up a hill. On downhills i always coast. At lights that are obviously long (just turned red), i turn my engine off. I try to drive around 40MPH whenever I can. On highways, dont exceed 60MPH and try to keep a constant speed: dont brake and accelerate all the time.