I can get 18.2mpg at 65mph throughout the entire tank. 65-74 I get 16.8 - 17.01mph. This was over a 2,500 miles. I don't go over 75mph and my RPM's try to stay under 2,500. The mountains of WV the Northern Michigan kind of made that hard at some points.
5w20, stock wheels & tires, Camping loadout, 18 days of driving,
I have no reason to believe anything greater than my numbers can be normal unless your motors are so loose, they're about to give out.
Things to consider, Pumps are often wrong. Math does not lie too often but we do fool ourselves.