I follow the fuel use closely and when new, my tractor used about 1.1 gallon per hour for general use and 1.3 GPH for high RPM rear Frontier RC2048 Mowing. I track it for expense purposes and cost estimating.
Now, with the tractor broken in, synthetic fluids, treated fuel and no Biodiesel and using cetane enhancement, etc, I very consistently use .7 to .8 gph for non PTO work and .9 to 1 GPH for PTO work. Snow plowing, the fuel economy is very consistently right at .8 gph with the average engine RPM's at 2,500, sometimes, briefly WOT running down the road between driveways.........
This is with the Mauser cab (which adds about 430 pounds total) , 800 pounds of 3ph ballast when the mower isn't on and with the Versa Turf radials...............Also, being new, you will notice the last half of the tank goes much faster than the first haf of the tank. So if you are watching clock hours, either on the HM or on your watch, the first half of the tank will last 4 hours and the last half will last less than 3 hours.
Don't trust the fuel gauge entirely because all of a sudden, the tractor will stumble and at that point, you are on walk......................Also, keeping the fuel tank full of fuel means less moisture in the tank, which means fewer problems for you and your tractor..............summer and winter.
Just yesterday, I spent $230 buying mowing gasoline, which will last me about 50 hours of mowing ($230/$3 per gallon = 76 gallons of gas,using about 1.5 gph mowing), or about a month this time of year......mowing 5.5 hours on each Thursday and Friday afternoon.
Diesel fuel, I spend the most in the winter, plowing snow. I am still burning the last 15 gallons of the 60 gallons of diesel I bought in November.