Grizzly 450 EPS fuel range

We got a 2014 Grizzly 450 EPS for my wife to ride, and took it out on its first trail ride today. We rode REALLY slow since it was the first time my wife had ridden an ATV in a while and I was carrying our daughter for the first time on my machine. We rode 29 miles, and it used maybe 1/8 of a tank of fuel on the gauge. Like I said it was really slow (15 probably, maybe 20 mph at times) and very flat. I haven’t got a chance to refill it and compute the mileage, but its nearly useless since it was so slow and flat.

We are heading to Utah on an ATV trip in a month, and I am wondering what other 450 owners get for mileage when riding them in their particular conditions? The carburetor plus the 4.0 gallon tank worry me. My machine has a 5.7 gallon tank and EFI ( a 2014 Arctic Cat 500 ) and I have 80 miles on the tank and its just under half on the gauge. Computing my mileage will be slightly more useful because the first 45 miles on the tank I rode rough terrain, got on the gas good and enjoyed the machine as it was supposed to be!!

I am looking into Rotopax for one or both machines, but don’t know what I need. Here in Minnesota I don’t worry too much about the extra fuel, but trips like our Utah trip make me feel more secure since her fuel tank is so small. I would appreciate any input!!