Light. Sometimes fumes.
Why make travel so boring and predictable? Why not make even routine trips interesting? Will I make it? Or will I get in trouble?
I take a racer's approach to it. The fewer stops I have to make, the less time I waste on pit-in and pit-out. I might as well maximize the distance I get in between fuel stops.
In each of my vehicles I know how many gallons are left when the light winks on. So I have a rough idea how many miles I've got left before I'm hoofin' it. I just make sure I fill up before I've hit that distance. Useful to know in those rare occasions when I'm in BFE or running really really late and need to know if I can make it to my destination or not on what I've got left.