1/ I assume you're playing mods, since for vanilla escorting craft doesn't make much sense (because UFOs don't attack)
2/ The fuel consumption in OpenXcom does not depend on path length... very important to understand here. The (classic) fuel consumption depends on craft maximum speed. Therefore each mod that is using the Hunter-Killer functionality should rebalance the speeds and fuel capacities of its transports and interceptors to allow seamless escorting.
I have allowed decreasing fuel consumption while escorting... but not less than 50% of normal fuel consumption (which is same as when patrolling)... otherwise it would be very easy to cheat the normal maximum craft range... which we don't want of course.
The (special) fuel consumption (e.g. when burning Elerium-115) depends only on time, 1 fuel unit every 10 minutes... so any craft burning non-classic fuel need to be also rebalanced accordingly.
PS: I am of course open to more suggestions and ideas, but they have to be compatible with vanilla calculations...