You may see all of the cars scattered around Muldraugh or elsewhere and wonder, what about the gas in these cars? Well don't worry, you can get that gas from those cars and even gas stations if you have an empty gas can. Here's how you can siphon gas from a car that has gas.
1. First, find yourself an empty gas can. These can be found in garages and gas stations around the map.
2. Once you've gotten yourself an empty gas can, find a car with gas in it. You can either enter the car and view the gas guage, or simply see if the siphon option is there by pressing V
next to a car.
3. Click the Siphon Gasoline button, and your character will walk over to the gas hatch and fill the container.
4. Your empty gas tanks will now turn into gas tanks, which you can view how much is left by hovering over them.
That's all you need to know about siphoning gas in Project Zomboid. You can fill as many gas tanks as you would like, then fill up your car with it. It's recommended to hotwire the car first, so you'll have full control over the car.