Today , 41 deg F in Naperville , 40 in Wood Dale. Here's a funny story : When I got home yesterday , the range (miles remaining) read 219. This morning , after driving 35.1 miles , it only went down by 30 miles , to 189. My morning route (23 miles highway , 12 miles surface streets ) in cool-ish weather doesn't give more than about 60 MPG. How the heck do they calculate "range" , anyway ? Is it based on the tank ? The previous trip ? 35.1 miles , fcd = 60.9 x .956 = 58.22 MPG. Tank is at 407.3 miles , 60.13 MPG.