[YMAA]

Just out of curiosity, what brand of gas do you use? I used to fill up with 93 gas at a station owned by a small chain out here, but after I filled up there for a while my mileage started to tank like crazy. I have a mostly highway commute and I averaged about 23-24MPG over the past few months. A few weeks ago I started filling up at a station with ethanol free 91 and my mileage went up by about 1-2MPG almost immediately, and is steadily improving. I assumed that because the gas was labeled 93 it'd be fine for the car, but the station must be using cheap gas or may need to clean the tank. The car seems much happier on the better quality 91.

On a somewhat related note the car started throwing codes related to the fuel pump and rail pressure sensor on startup about 2-3 months ago, which I assumed were due to a mechanical or electrical problem. I switched to the ethanol free gas as part of my own troubleshooting of the issue, and in addition to the increased MPG my startup issues went away completely. Between the increased MPG and reliability I'll happily pay a few cents more per gallon.

If you don't think your driving style is part of the problem it could be the gas you're using.