What kind of driving will you be doing to expect a 50 MPG average? My driving is about 85% highway and my lifetime average is down to 49.9 MPG. I can't complain, and am looking forward to warmer temps to drive that lifetime average up. I'm hoping to have a 52 MPG average by the end of October of this year.
The problem you will see is that the extreme cold weather really hurts these cars. As long as you are experiencing temps under 20*, it's real hard to get much over 45 MPG.
Have fun and keep posting.
I'm hoping that I can exceed 50 mpg in the warm temps on the highway and then for the overall combined average I'm hoping to exceed 45. I still plan on running it hard here and there to keep the engine clean etc. Don't get me wrong though I'm pleased with what I've seen so far. My commute can be about the same mixture as yours (85% highway).