The last few tanks for me have been dissapointing as well. I typically get around 40 MPG, but the last couple tanks have been during rain/ice weather with temperatures between 25 and 45. The displayed averages have been around 38 and 39 MPG, which translates to around 36.5 to 37.5 MPG. I know it is not as big a hit as you have been taking, but my typical commute is 60 miles one way.