Although I have a V8 with the 3.42 gears, mine averages 15-15.6 in the winter, and 16.6-17 summer. I have a pretty heavy foot as well. I dont really do any type of warm-up either, other than the time it takes for the garage door to open. When at work, I start her up, wait for the idle to come down a bit, maybe 10 secs, and drive off.