Again, I state you really can't go by the computer readout, it's not very accurate and even less accurate if you reset it at each fill-up. As suggested by BPD to get the most accurate reading don't reset it, leave it continue to calculate without resetting, it will get more accurate.
Now, I've kept records on fuel useage since I've had the car, and I average about 22mpg overall. I have gotten a high of over 30 and a low of about 14. If you want to keep a running record that will calculate and help you see your patterns, try Fuelly.com. I use it and love the detail it can show. But I've been keeping accurate fuel records for years. If you fill the same amount at each fill-up and calculate the old fashioned way, miles traveled divided by gallons used, it will give you the most accurate fuel use, if you fill to the same level on each fill-up, and over time you will get a true picture of your fuel useage.
