You give him/her your car keys.
Or if you are married to them they have their own set.
They head out using your car that has enough gas to get you to and from work for the next 3 days.
The next morning, you get in the car and there is just barely any gas in the tank.
The light indicating you need gas comes on half way to work.
“You have enough to go 30 miles when the light comes on.”
Yeah, IF you don’t have to sit in bumper to bumper traffic on the highway due to some moron on a cell phone rear ending a semi!
Single means there is ALWAYS the same amount of gas in your tank as when you last parked the car!