On my return trip from San Diego I did an Iron Butt and pretty well stayed 85-90 from Bakersfield to Tacoma aside from the nasty bit in the Siskiyou's. I stayed in the low 30's for mpg. It was also cold/wet and generally unpleasant for the last half. It was below 50 degrees almost the entire trip and I seemed to remember hitting 28 degrees when I summited the pass.