01 Silverado Gas mileage

[Botlfed]

I'm just curious how odd is it that my 01 Silverado gets at a constant 18.x miles per gallon.
It has a 4.8 4l60e and 3.42 gears and 17" Gmc wheels. Oh and that 18.x is mixed driving.

not odd at all, my 07 ccsb gets 21 hwy 18-19 city.