I went on a leaves run and came back with enough fuel for around 10 more hours. We may be in different areas, but mine is covered in leaves, plus I found a bunch of wood along the way. Also, keep in mind how much power you're consuming. You can throttle your generators to use less fuel (and therefore have less output). Either count up how much wattage you're using on a single generator, or just keep reducing the % until it shuts off and then you will know your current output threshold. I halved my fuel consumption by doing this.