I know there are senarios that have you fuel up your diesel locomotive,but is it even possible to run out,i don't ever recall running out,are there working fuel gauges on diesel locomotives,maybe that's a possible reason why locomotives just stop,its not a brakedown,your just out of gas.
Don't think they have designed it to ever run out. Just giving us the experience of filling up the tanks. Would be a pain in the ass finding a fuel pump on that map!
They're refilled as part of their maintenance routines, as you do yourself in some of the scenarios. Real world operators would never dream of letting a service run out of fuel, so there would be no need to model it, I suppose.