A lot of vehicles have 'reserve' fuel, where the meter simply doesn't read the last ~3-5% percent of the fuel tank, so you think you'll be out sooner and choose to visit a gas station before you actually end up stranded.

I've also grown up in snowy mountainous regions and been taught anything under 1/3 of a tank is considered empty. Always keep reserve fuel so you have heat when/if you get stuck in the snow.