All the above discussion is why I pay for all of our RV gas with a credit card that rebates me back about 17-18 cents per gallon everytime I cash in it's reward points. About once a year the total reward points turn out to be real money.
By the way, for several years ending this past Sept., we have traveled to WA at least twice a year. From what we saw, WA gas wasn't anywhere near 40 cents per gallon less than in CA. 15 cents per gallon, maybe, but not 40 cents per gallon. The additional gas tax in WA will bring it's fuel prices fairly close to CA fuel prices from what I can tell.