We actually have off-road diesel for this. Alberta also used to have "purple gas" but it was halted in 1999 due to rampant abuse. We could do something like that, but it hasn't worked historically.
Also, don't forget about Mt.Shasta, and Mt.Lassen in Northern California, which are part of the Cascade volcanic ark Mt. lassen erupted in the early twentieth century. Mt. Shasta has active steam vents at it's summit, last erupted in the eighteenth century, and has a major interstate highway, along with a handful of small towns sitting alongside it's base.