Because I have driven on this road sooo many times, I thought it might be interesting to post this. To make the trip interesting, I like to see what MPG I can get out of a car. The winner is no shock. Temperature does play a part in the MPG. I have gotten 28 MPG in the IS-F rolling at 60 MPH in cruise.
Lexus IS-F (800 miles on the clock)
Seattle to Coeur D Alene, Idaho and back @ 70 MPH in winter = 25 MPG (673 miles)
Lexus IS250 AWD (15,000 miles on the clock)
Seattle to Spokane and back @ 70 MPH in fall = 31 MPG (586 miles)
Infiniti G35 2007 (10,000 on the clock)
Seattle to Spokane and back @ 60 MPH in winter = 27.1 MPG (586 miles)
Prius (25,000 on the clock)
Seattle to Spokane and back @ 60 MPH in summer = 57.7 MPG (586 miles)
Prius (15,000 on the clock)
Seattle to Spokane and back @ 60 MPH in winter= 47.3 MPG (586 miles)
The 586 is the same because when I got to the house I was visiting, they did the driving. Just incase you are suspicious like me.
Now back to reality. My work commute is stop and go between 35 MPH and 50 MPH. 12 miles each way. On a cold morning, I am doing around 17 to 18 MPG. On the way home if the sun is out and I can control myself

, 21 MPG.
It is interesting to compare to my G35. I had to struggle to get in the 20 MPG on average. Yet for this monster IS-F, I have a fighting chance.
PS Gas in Idaho was $2.16 premium this weekend, $2.55 in Seattle. hmmm.