yep... in Hard Times, too
only instead of g-hours, they used g-turns
It also depends on turn length, if you use some other turn length
by determining how many g-turns of fuel there are, figuring how much fuel used in combat isn't hard. If you used 4-g's of fuel in a single turn, you used 4 g-turns of fuel
if you used .1 g's over 40 turns, you used 4 g-turns, too
It makes space combat a bit more tactical too
Should you evade, knowing it could mean you can't maneuver later at the rate you want?
If you're too low on fuel, you might not be able to evade those incoming missiles, especially if you're on an outsystem vector... what good is winning the battle if you're lost, to float out-bound?
Missiles might even be launched simply to force the opponent to use up their fuel.
( I tend to use a variant of "Fusion Guard" by Bruce Macintosh, a ruleset I found on the 'net a few years ago. You have to allocate g's to maneuver, evasion and aiming for spinal mounts. I don't know if it's available anymore. )