I have a 2008 and I usually only get 44-46 MPG but on a few rare occasions it will jump up so high it almost scares me. Yesterday I had the heat and fan on (but not high) and the next thing I know the MPG is almost 70 MPG! This has happened before. I had filled up the tank the day before but my MPG was not extraordinary afterward. Later yesterday, after parking for a few hours, it came back down to its usual 44-46 MPG. Is there a glitch? I was not driving anywhere different. It is just perplexing. Any thoughts? Thanks.