When driving highway, doing 75 on cruise (I dont hypermile), I can easily get 500-550 as well. My only 2 trips even remotely like this have 520/13.5gal and 527.5/12.57 (my best trip for 42.0mpg tank average). I have a heavy foot, and drive between 75-80 when traveling on the highway (not pulling), I can only imagine if I actually slowed down, but the A3 easily w/o trying can average 38-42mpg doing 75mph. During the summer I idle alot, typically pull a waverunner on the weekends for trips(idle at the docks for lauching etc etc), and do mostly driving around town (hope on I for exit jumping). My overall average since owning the A3 has been 37.5mpg over 10k miles. I have done two long trips up to my brothers with the waverunner, so roughly 20% of my miles have been pulling a waverunner (492 1-way)