How to Siphon Gas From a Car

Knowing how to siphon gas from a car or other vehicle is an important skill, but it isn't taught as often as it once was. Unfortunately, since most people associate siphoning gas with stealing (since siphoning gas from other people's vehicles without their knowledge is very much illegal), it's a skill that many people have chosen not to teach their kids. 

Unfortunately, siphoning gas can be important in an emergency, during long road trips, and even as a regular part of maintenance and winterizing your vehicles. 

With those things in mind, you must know how to siphon gas from a car. That being said, please don’t use this knowledge to steal gas or to engage in other morally questionable activity with someone else’s vehicle.

When Is Siphoning Gas Useful?

There are a lot of circumstances where knowing how to siphon gas can be a potentially useful skill. The two most common are for winterizing vehicles that are only used seasonally or removing gas from a car that needs an empty gas tank to safely and properly repair.

In both of these circumstances, you'll want to remove the old gas from the tank because gas can separate over time. The longer the gasoline is separated, the worse it's likely to be, both for gas performance when used and for the gas tank and fuel system in your car. 

Unsurprisingly, gas is a relatively caustic material that can cause damage to your gas tank when it’s left sitting for too long. The separated gas components are also similarly caustic and can cause even more damage than the gasoline itself. 

Siphoning can also be useful if you're ever stuck on the side of the road without a gas station in sight. Emergency help services might be able to come to give you a lift to the closest gas station in some circumstances, but not every state can send highway responders to the more remote areas of their state. 

If helpers aren’t immediately available, your best bet may be siphoning a couple of gallons off another vehicle, particularly a friend or family member who may have been following you. Otherwise, a helpful driver may stop and be willing to give you enough gas to get you to the next gas station down the road. 

You may also need to siphon gas out of a vehicle if you know that the gas has been contaminated or to perform certain kinds of vehicle maintenance. 

The Different Ways to Siphon Gas

There are three basic ways to siphon gas, though they are all variations on a similar process. Choosing the right method (and preferably the safest!) is incredibly important for preventing damage to your vehicle and its fuel tank and keeping you safe. 

With that in mind, we’ve listed the possible methods from safest to most risky. If possible, try only to use the first method since the other two options introduce greater risk to your health. 

Siphon with a Professional Siphon Tool

There are professional tools designed specifically to siphon gas out of the fuel tank for maintenance purposes. These tools are universally the safest option, and they are usually also the most efficient. Professional siphons are also typically a better option for new vehicles since newer cars have protection systems that help prevent siphoning while also protecting the gasoline from contamination in the fuel tank. 

Professional siphons come in various sizes and lengths, but they all come with a reasonably long tube with some kind of hand pump attached to the tube to help get the siphon started. The hand pump can come in various types, but most are single directional pumps designed to pull in a specific direction. 

Fortunately, it’s easy to tell which side you’re supposed to put in the gas tank because there will be different nozzles for the gas tank and the container you’re siphoning into. 

Simply insert the gas tank nozzle into the tank. You’ll need to make sure it’s relatively deep to make sure it's in the gas and near the bottom of the tank if you want to drain it. Insert the other nozzle into your gas canister and place the other container on the ground. It’s essential to make sure your gas container is lower than the fuel tank for the gas to siphon correctly. 

Once everything is positioned correctly, use the hand pump to get the siphon started. Once gas starts flowing, you can let the siphon work on its own. It doesn’t need the pump. 

If you only need to siphon a small amount of gas, make sure you’re keeping a close eye on the gas canister, so you know how much you’ve siphoned from the fuel tank. 

Air Pressure Siphoning

If you don’t have a professional siphon, but you have a relatively long tube or two different siphoning tubes, you can use the air pressure siphoning method. This method uses two separate tubes to increase the air pressure in the fuel tank and allow the gas inside to flow into your fuel container. 

You’ll also need a rag or a piece of flexible plastic to cover the fuel port around the two tubes so that you can increase the air pressure inside. If you’re using fabric, it’s best if you can get it slightly damp so that it creates a better seal and doesn’t let as much air through the opening. 

With this method, you'll insert both tubes into the fuel tank, and you'll insert the other end of one of the tubes into the gas canister. Use the end of the other line to blow air into the fuel tank until gas starts flowing. Then plug the tube with a thumb or finger. You may need to add air to the fuel tank several times, depending on how much gas you need to siphon. Try to blow with your mouth, not your lungs, to minimize gasoline fuel exposure risk. 

Mouth Siphoning

This method is undoubtedly the most dangerous. Unfortunately, it's also the method that's best known and most commonly used on TV. 

Mouth siphoning should only be performed when there is no other choice, like if the tube you have on hand isn’t long enough to cut in two for the air pressure method. 

With mouth siphoning, you’ll insert one end of the tube into the fuel tank. Place your fuel container on the ground in front of you, and then use your mouth to pull gas out from the tank and into the tube. Monitor the tube carefully, the gas will move quickly, and you don’t want to get any in your mouth if possible. Quickly plug the tube as soon as you see gas coming up and transfer the end to the waiting fuel container. 

The siphon should continue working on its own until the fuel tank is empty or the fuel tank’s pressure is equalized with the gas in your fuel container. 

If you accidentally inhale gas fumes or get any gasoline in your mouth, contact poison control immediately. Under no circumstances should you breathe or swallow gasoline since gasoline poisoning is severe and requires immediate medical treatment.