Hey! Just saw your message. Mine's an 09 - depends where I'm driving though. If it's just straight highway I average near 30 mpg most of the time - but otherwise going 85 mph and slightly uphill it'll go down to about 25... From WY down to CO I think it's slightly downhill, and have averaged 33 before. Have studded tires on it right now and mileage from CO back up to WY dropped a couple mpg - you can definitely get over 27 though, just don't accelerate too hard (annoying, I know!!!)
In all honesty, I have no clue how it happened. I made the exact same trip this summer and between the two same points I only averaged about 29-30 mpg. I think it was just a giant one time fluke.