only recently was it removed, because cars would just stop working and no one knew what it did.
you could never actually re-fill your car and everytime you respawned the car, it would give all your fuel back.
IN MY OPINION, if it returned, it'd have to be fully implemented as so. Cars drain fuel from driving. Cars fuel amount is saved to stop respawning it to get it full. Gas pumps OR gas items to refill cars far away from the station.