I was thumbing through the owners manual and on page 235 I noticed they list it as having a fuel capacity of 15.8 gallons, and under that they indicate that it has a "Fuel Tank Reserve" of 2.1 gallons.

I know a lot of trucks have a small reseve tank they can flip a switch to engage. On page 161 it states if the fuel reserve warning light comes on and stays on that "the fuel level is down to the reserve quantity of approximately 2.1 gallons."

What exactly does this mean, 17.9 gallons total capacity ?