An easy place to get this is the Cross a River challenge. Turn on All Wheel Drive and head straight out from the start. You can easily get yourself stuck just ahead in the first little bit of water and just keep the trigger held down for 5 minutes or so until 100L of fuel has burned off. If you’re not able to get yourself stuck in this spot, just drive around in circles with the trigger held down until you use up 100L. This vehicle is a gas hog so it shouldn’t take long. Don’t let up on RT until the achievement pops.