If that's all you're planning to do, then I don't think extra fuel is needed, but if it is 250 miles like doro stated, then maybe it would be wise. I have not done a round-trip from Green River. I've done five Maze trips with my 2002 (18.5 gallon tank, but holds 20 when filled to the neck from empty), but only took extra gas cans for one of them. I think my first trip in, which was with one friend, we topped off in Green River, drove to Panorama Point, Maze Overlook, and the Doll House, and out to Hite, all without extra fuel. He drove a T100 with a Four Wheel Camper topper, and both of our fuel lights were on about 10 miles from the marina at the end. We knew we'd be cutting it close, but figured we'd make it. Basically the only road we didn't drive in the Maze on that trip was Millard Canyon (44-mile round-trip spur). It was only on one trip where I included Millard and combined it with the Maze Overlook and the Dollhouse that I took extra. I can't remember if I needed it, but I must not have based on that first trip.
I can't help but shake my head with all of the jerry cans I see on various rigs here in Colorado. I think there is some peculiar fascination with the things. We are too developed and we don't have anything that I would consider remote, and the longest off-road travel without gas stations is probably in the neighborhood of 70 miles. The only other time I took my two jerry cans was for Death Valley, where I did need the extra 10 gallons to avoid paying the insanely inflated price in the park. The only other place I would consider taking extra fuel would be for Nevada, depending on the network of roads planned.
