When you have the game set to display gallons, the active task on the right side of the screen displays in gallons, but the menu in the top-left of the screen displays in liters. In the screen shot the mission is telling me I need 476 gallons, and the UI menu in the top-left is telling me my trailer has 2800 liters. I have to constantly do the calculations manually to ensure I have enough water in the trailer.