You are right about the high fuel prices along 395 until you get way South into AZ.
Our home base is Reno and when we leave to go to Casa Grande for the winter we appreciate our aux tank which gives us a little over 100 gal. of diesel on board. With that we prefer going over the Sierra's on 80 into CA and down thru Bakersfield then to Casa Grande. We don't need fuel along the way and get to take advantage of the cheaper prices when we get to our destination.
Last winter we filled up before our return to Reno for $3.29 taking advantage of a .30 cent discount for buying groceries at Fry's.
You learn to play the fuel prices.