how to siphon gas

How to Siphon Gas Out of a Car

There are many reasons you may need to siphon gas out of a car. For instance, you may be on the road and far away from a fueling station then you may want to siphon gas from another car. This will help both the cars get to the gas station and refuel.

The other reason may be that you want to drain out the car before you store it away for the winter. You may have two vehicles and want to transfer fuel from one to another. Or you may need gas to run a generator or other appliance during a power outage. The fuel in the tank may be contaminated. And you may need to remove it before refilling.

Before bad gas meant that the fuel was years old and contaminated with water and solid debris. Nowadays there is ethanol enhanced fuel (15% ethanol and 85% gasoline) that causes problems in all types of engines that may go bad in a few months.

Science Behind Siphoning Gas Out of a Car

It is advisable to travel with a siphon pump, a can, and some rubber or plastic tubing in your automobile’s trunk. How to Siphon Gas Out of a Car? 2020This way you will not have to use your mouth for this purpose.

You can siphon gasoline from the tank due to air pressure, liquid cohesion and gravity. Siphoning involves inserting a hose into the fuel tank. The tube end dipped in the fuel tank is higher than the tube end in the can.

The air pressure in the tank forces the standing fuel into the hose or tube that eventually flows through the tube and out of the other end. This is due to the cohesive flow of liquids. One molecule of the liquid sticks to the other and the wall of the hose.

The gasoline starts to flow and continues to flow under the influence of the suction you provided at the other end and this cohesion. You can speed up this process by using a pump that creates suction at the exit end of the hose.

The latest automobiles feature roll-over values that relieve pressure in the tank. They also prevent backflow and also prevent siphoning. Thus, the traditional methods of siphoning may not work and may even cause damage to the vehicle.

So, to siphon gasoline from the newer models of automobiles it is recommended you use a pump with hoses of a small diameter. The working principle of these pumps will be the same as older ones.

The Hazards of Siphoning Gas of the Car

It is best to practice the siphoning methods using water before you try it on the actual gas tank. Do not siphon fuel unless it is imperative.

There are many reasons for these suggestions;

Inhalation the gas fumes – The exposure to the fumes causes harm to most organs in our body. Direct inhalation of gasoline fumes can cause lung damage and carbon monoxide poisoning.

Choking on gasoline – While siphoning gasoline you may take it into your mouth. This may cause coughing andHow to Siphon Gas Out of a Car? 2020 choking. If the gas goes down the wrong way i.e. into your lungs it can cause lung ailments. Gasoline is an irritant to the lung tissue. The oil may coat the inner lining of the pulmonary system and affect the oxygen-carrying capacity of the blood. Depending on the quantity swallowed it can have deleterious effects on the entire body leading to poisoning, coma, death, and respiratory arrest.

Dizziness and nausea – Breathing in the fumes can cause fainting, nausea, dizziness, and in extreme cases brain damage. Keep this in mind when you attempt to siphon fuel alone on a deserted highway.

Gasoline poisoning – happens when you swallow it. The oil is toxic due to the presence of organic compounds such as alkanes, benzene, cycloalkanes, alkenes, and other aromatic hydrocarbons.  Besides, there is lead in the fuel. You may require medical attention if you begin to feel sick.

Risk of fire – If you do not handle the fuel correctly. You may spill it, drip it, or soak your clothes and the upholstery of the automobile in it. Be careful of open flames, smoking cigarettes, and tinder. Besides gas fumes can catch fire in high static electricity too. Handle the fuel with the utmost care and drain the tubes and pump properly before storing it. Keep sand, mud ashes close at hand. Woolen blanket and wet rags can be used to smother the fire. If you have spilled a large amount of fuel then a deluge of water should smother it.

Methods of Siphoning Gas Out of a Car

Siphoning is a skill that you may require in any situation where you have to transfer a liquid from one container to another. It works by creating a vacuum that initiates the flow of a liquid from a higher point to a lower point.

Method 1: Manual Suction Method

Materials needed – a length of tubing or hose to extend between the fuel tank and container.

Procedure – Open the gas tank by unscrewing the gas cap. Now feed the hose into the tank. Ensure that it is dipping in the fuel. Next, open the container that is to be filled. Now suck at the other end of the hose. The process is similar to drinking juice using a straw.

It is better to use a transparent or translucent hose. You will be able to see the liquid rising towards your mouth. As the meniscus rises towards your mouth transfer the end of the tube to the canister. The gas that would have How to Siphon Gas Out of a Car? 2020entered your mouth now falls into the canister.

Just in case the gasoline enters your mouth, spit it out and rinse your mouth thoroughly. Keep the container lower than the fuel tank. This will drain the tank easily.

The other smart variation of this method is to use a transparent or translucent tube and loop it in your hand. When you see the fuel rise into the loop in your hand. Place a thumb at the end of the tube to hold the fuel at that level. Then carefully tip the end into the fuel can. Let gravity do the rest.

When you have a siphoned sufficient amount of fuel clamp the end of the pipe shut. Then raise this end higher than the fuel tanks level. This will drain off the gas in the tube back into the fuel tank. Then shut the lid of the tank.

Method 2: Air Pressure Method

Materials needed – Two lengths of tubing of 1/4 to 3/8-inch diameter, a gas can, rag, or soft material. Optional – You can blow into the tank or use an air compressor or pump.

Procedure – Insert the long tube into the tank such that one end dips in the fuel. Next, hold the shorter tube in your hand next to the longer tube in the opening of the fuel tank. Now seal the mouth of the fuel tank such that the rag holds both the tubes in place.

This air-tight seal helps the build-up of pressure in the tank. When you blow into the tank the fuel is pushed into the longer tube due to high-pressure building in the tank. You can use the power of your lungs to generate this pressure in the fuel tank or you could use an air compressor or pump to do this.

If you are using your mouth then do not inhale from the tube this may cause you to take in fuel vapors. If you want to take a breath; use your thumb to seal the end of the tube. The thumb holds the pressure in the tube preventing the fuel from flowing back.

Once the flow of the fuel into the can starts there is no need to blow into the shorter tube. The fuel will continue to flow until the fuel is drained. The other two eventualities may be that the tube develops a kink or it is removed from the tank.

After you are done siphoning fuel. Raise the level of the tubes higher than the fuel tank. This reverts the flow of the fuel and prevents dripping. Then remove the tubes and the seal-plug from the tank. Next, screw the cap on the fuel tank.

Method 3: Using a Mechanical Siphon Pump

Materials needed – Gasoline can and Siphon pump.Suction pump

Procedure – The mechanical pumps work like manual sucking but they protect the operator from the ingestion of gasoline and the effects of its fumes. This is the most reliable and safe method of siphoning.

The siphon pump has two pipes made of metal, rubber, or plastic attached to a bladder. The bladder can be pumped by hand or piston to create suction. The piston may have handles like on a bicycle. These are anchored to the ground and pumped like a bicycle pump. Or the bladder can be squeezed like a blood pressure meter (sphygmomanometer).

Identify the input and output tubes of the pump. Then insert the correct one into the tank. Otherwise, you will blow air into the tank instead of drawing gasoline. One of the tubes or pipes goes into the tank while the other is placed in a collection tank or can.

Ensure the tube in the tank is dipping in the fuel. If you do not want to use a hand pump there are electric and battery-operated siphon pumps in the market. Now start pumping – you can squeeze the bulb or pump the piston, etc.

The gasoline will flow from the tank into the can and you can see the liquid flow. Continue the transfer until you have the desired quantity. When you are done – raise the output end of the tube to drain the fuel into the tank.  Then cap the fuel tank. Ensure there are no drippings. Clean the pump and store it as per the manufacturer’s instructions.

Method 4: For Modern Cars

Materials needed – Suction pump or 1/4-inch tubes, screwdriver, or wooden sticks.

Procedure – Modern cars have a siphon-proof value or filter built into their fuel tanks. This valve is a metal flap that clamps shut to prevent the hose from entering the fuel tank.

To siphon gasoline from the tank of a modern car you can use the manual suction method or the pump. But for Suction pumpany of the methods to work the valve or flap has to be held open using a chopstick or a screwdriver.

The wooden object is highly recommended as metal objects may cause a spark that may cause the combustion of the fuel vapors. Wooden, rubber, or plastic objects would ground the charge on the car’s body to prevent the electrostatic charge from building up.

Wedge the chopstick in place and insert the 1/4-inch hose or tube. Some cars have a ball-shaped valve that prevents the entry of tubes or hoses. There are siphon pumps in the market that can be used to siphon such cars.

They have a thin pipe that passes into the tank through the space around the ball-shaped valve. the rest of the pump is like the regular ones.


In conclusion, there are many ways to siphon fuel from your car and the dangers associated with them. Gasoline is highly flammable and it also has deleterious effects on one’s health when ingested or inhaled. The vapors rising from the tank can be dangerous too. There are the gravity siphoning method using tubes and a can. There a manual, electric, and battery-driven pumps. You can draw around a gallon in 8 – 10 minutes using the gravity siphoning method. You may half the time by using a manual pump with a bulb or piston. The electric or battery driven ones may quicken the process to around a minute. It is recommended you use methods where you do not come in contact with the fuel and the electrostatic charge is grounded. This minimizes risk to your life and health. Thus, the use of manual pumps is highly recommended that can be carried in the trunk. Besides they do not need a power source too.

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