Stop in for a cup of coffee

Ddaddy said
Then there is something seriously wrong with your vehicle.

When was the last time you changed the plugs? The 5.7 requires new copper core plugs every 30k miles..

In February.

Ddaddy said
And the tank level on the gauge is irrelevant. What were the MPGs? Did you fill up again at the same station and pump and check it?

Roughly 11

Ddaddy said
Sooo...29 gallons for a 300 mile ride? That’s less than 11 mpg. Something isn’t making sense.

it's all time 4x4 in a fully loaded Durango for starters.