We just did a trip from California to Alabama (5k miles for the trip MPG is what the truck stated not calculated on miles and gallons) and back we took I80 on the way there and 40 back, all freeway except get off and eat or get gas.
Best gas mileage was in Nebraska I opted for the 88 octane no ethanol gas the speed limit was 75 to 80 we were driving 80 to 85 and I got 21.9 on that tank.
Worst gas mileage was when we filled up in Texas I got 16.9 and driving 75 to 82 the very next morning when we did a partial fill up in New Mexico it jumped up to 18.5
Average on the freeway is usually 18 to 19 mpg I drive 70+ though
2016 TRD Off road double cab stock no bed cover
started trip with fresh oil change
The gas in your state has a big part in the mileage, or in California it does between winter and summer gas my mileage varies