Originally Posted by JARblue

After about 25K miles of daily highway commute for the wife, the Z became my DD. She averaged around 21.5 mpg for the life of the car. My commute is city miles, but I avoid highway traffic by taking alternate side streets. For about 10K miles, I got no more than 18 mpg unless I was really trying to get good mileage - I struggled to get 300 miles on a tank filling up at least 17 gallons 95% of the time. I got an EcuTek tune in May and I've put over 5K miles on it since. I'm now getting 20 mpg on my daily commute and 350 miles per tank without trying (with the same fill up habits - 17+ gallons each time) When I take it out to have fun, I typically get 12-15 mpg.