SINCE I have had my Prius 2010 Model my MPG has been at 44-45 City, 47-50 Hwy. Up until recently things have been really good then I had the new software update and I swear on the hwy I cant get over 38 MPG. I went back to the dealership and they told me nothing was wrong that I should drive in ECO mode more and so on. I have lost 70-80 MPG per each full tank of gas. Any advice on what the heck is going on?