Remember, my example was also using the first year of the 500, in the first year the "new" automatic was available. We were also riding A) at high altitude (8,500-9,700 feet asl). B) Either very fast (max speed), or very slow (2-4 mph). C) Double (driver and passenger). D) With the optional factory racks that weighed 90+ lbs each, and 100 lbs of extra gear and fuel.
Also remember - that transmission was completely redesigned a year, or two later. Too many people complained about the fuel mileage, sluggishness, and the feeling that it never locked up (always sucking extra engine rpm). And... the ATV model I'm using as an example here went on a weight loss program a few years later, as well. Again, too many people complained about the weight and center of gravity. It often required half a dozen people, or a truck to get one back on its wheels, once it was flipped (the one I road weighed in at almost 900 lbs {I had a Toyota Starlet that weighed only 130 lbs more than that ATV}).
The major issue with fuel economy on the early 500s was the lost revs. The engine would be screaming, and the bike would barely be moving (even when empty - not 10 lbs from max GVW like we were riding it).
So... My choice of using it as an example here was probably a poor choice. But, it was used, none-the-less.
Would it help, if I told you my brother's '86 Ford F250HD, Extended Cab, Long Bed, with a 460 ci V8 gets the same fuel mileage as my '04 Ranger?