SACNR utilizes a fuel system, meaning that any drive-able vehicle needs fuel. You can refuel your car at any time at any local gas station (marked by red flags on the mini-map). Police officers and medics have their fuel paid by SACNR Inc (only if they are using public service vehicle).

You may also buy gas cans which you can use to refuel your car on the go. Once your car hits 0% fuel, the engine will shut off and you will have 2 options - Leave the car or refuel with a gas can. Gas cans will add 25% of fuel to your car, which is more than enough to get you to the nearest gas station. You can hold only 1 gas can at a time.
At Regular Player Level 4, this limit is upgraded to 2 gas cans.
At level 8, the last upgrade to this limit is granted, at 3 gas cans.

A gas can can be used with /gascan (or "/gascan 1" for quick use). If the engine has shut off then you may restart it with /engineon. This will let you drive your car for a little bit distance to get to a gas station to refuel your vehicle. You can also press 2 on your keyboard and your vehicle will be automatically fixed and refueled.

Boats and aircrafts also have a fuel system, with the refill points located at airports and docks.