I have a 2019 RST with a 5.3 V8 gas. The fuel tank is 24 gallons. The fuel fill was clearly made for a diesel as it has a fill hole and a big open space for a def tank in front of the gas tank. I hate having to stop every 1.5-2 hours to fill up when I’m towing my camper knowing that there’s plenty of space for a tank with much greater capacity.