I was in Colorado, last week, and found that prices were 0.35 lower than what I normally pay (Bountiful).
The State tax on gas only account for 0.09 of the difference. Utah’s gas tax is 0.31; in Colorado it’s 0.22.
Although I didn’t but any gas in Wyoming, the posted signs indicated that gas was quite a bit lower there. (Gas tax 0.24).
Perhaps someone that is familiar with the industry can explain why neighboring states can have such a spread,