One ounce is the base unit in American and Imperial liquid measure.
One "cup" is 8 oz, and 4 cups to an American quart of 32 ounces.
Five cups to an Imperial quart of 40 ounces for 160 ounces to an imperial gallon.
For all the rest, one "cup" approximates 250 milliliters so 4 of those in a liter.
If I was travelling into sand dune country for photography, I could be all alone for a while.
On the floor in the back seat, I loaded 15 x 2 liter plastic pop bottles of water.
The wind was deceptive at +35C = sucked the moisture right out of you before you knew it.