When and How to Siphon Gas: The Complete Guide

Reviewed by

Richard McCuistian, ASE Certified Master Automobile Technician

Technical Reviewer at CarParts.com

Written by CarParts.com Research Team - Updated on September 29th, 2023

Reading Time: 4 minutes
Summary
  • Siphoning gas out of your car is the best option if you’re dealing with contaminated fuel, surviving during a power outage, and running out of gas in a remote area.
  • To siphon gas from your car, you’ll need a siphon pump. Place the hose in the fuel tank, and insert the other end of the hose into the gas can.
  • Old-timers would actually siphon gas by mouth, but this is a bad idea because of the dangers it poses.

News about thieves stealing fuel from cars isn’t new, but siphoning is more than a theft tactic. Siphoning can be helpful in various scenarios and even prevent problems down the line. So it’s crucial you know when and how to do it.

When to Siphon Gas

Taking gas out of a car is your best option in the following scenarios:

Dealing With Contaminated Fuel

Contaminated fuel can damage your engine and lead to costly repairs. The best way to prevent such problems is to remove the contaminated fuel via siphoning.

Surviving During a Power Outage

If there’s a power outage in your area, you might need your vehicle’s gas to power your generator. Siphoning the gas, then using it to power your electrical devices, is a fallback for emergencies.

Running Out of Gas in a Remote Area

Getting stuck in the middle of nowhere with a shortage of gas supply is a recipe for disaster. If there’s a car nearby with fuel, you can transfer its gas to your ride’s tank can be a lifesaver. Of course, don’t forget to ask for permission before siphoning.

How to Siphon Gas

Siphoning is a tricky process that transfers liquid from one container to the other. It works by creating a “vacuum” to displace the fluid.

Before you consider siphoning gas, take note that newer vehicles have a block at the base of the fuel filler neck designed to prevent a hose from being pushed into the tank to siphon the gas, so shoving a hose into the tank may well be a non-starter on your particular vehicle.

Siphoning is a tricky process that transfers liquid from one container to the other. It works by creating a “vacuum” to displace the fluid. Here’s how to do it:

Place a Gas Can Near the Tank

Make sure the can is clean and uncontaminated. If it isn’t an emergency, you can buy one at a local hardware shop.

Get a Siphon Pump

This process wouldn’t work without a siphon pump, as it creates a “vacuum” to seep fuel out of the gas tank.

You can use a manual or automatic siphon pump. You’ll need to pump the former several times to such the fuel out, while the latter makes siphoning as easy as pressing a button.

Place the Hose in the Fuel Tank

This step can be tricky because new cars often have small fuel-filler openings and spring-loaded flaps to stop fuel vapors from escaping. Again, most new vehicles have a blocking mechanism at the bottom end of the filler neck to prevent pushing a siphon hose into the gas tank. If you’re unsure how to insert the hose, consult the pump’s manual.

Insert the Other End of the Hose Into the Gas Can

Make sure the end of the hose is pointing down. If you’re using an automatic pump, the fuel should flow out of the gas tank and into the can. Otherwise, you’ll have to pump a few times to get the gas flowing. Keep in mind that the receiving container needs to be placed lower than the inlet of the hose where it’s in the tank or the fuel won’t flow.

Consult your pump’s manual for the exact steps on how to use it. Make sure to secure the hose and submerge it in the fuel tank to keep air from ruining the process.

Elevate the Hose in the Gas Can Once It’s Full

This will stop the flow and make excess fuel seep back into the gas tank. Afterward, remove the pump carefully. Don’t forget to seal your gas tank again after siphoning fuel out of it to prevent contamination.

Other Ways to Siphon Gas

Aside from using a siphon pump, there are other ways to seep fuel out of your vehicle’s tank.

Note from Richard McCuistian, ASE Certified Master Automobile Technician: Old timers would actually siphon by mouth, but this is a bad idea. Note that this is not recommended for the dangers it poses, but if you absolutely have to do it this way, have a piece of clear hose on hand such as you can get at some hardware stores and online.

Using a siphon pump is the best way. However, with the clear hose, you can see the gas coming and get your mouth out of the way before it begins flowing out of the hose. Remember: the outlet of the hose needs to be lower than the inlet.

Again, we do not recommend this process because it’s dangerous, as you might swallow gasoline or inhale its vapors.

What Is an Anti-Siphon?

Some new vehicles come equipped with a rollover valve, which lessens tank pressure and stops back-flow. However, these valves also prevent siphoning.

Moreover, some new models also have an anti-siphon mesh screen at the higher part of the fuel pipe. The screen prevents anyone from feeding anything solid into the gas tank, including siphon pumps.

How to Siphon Gas from a Car with an Anti-Siphon

Generally, it’s not recommended to siphon gas from your car if it has an anti-siphon—unless it’s an emergency. After all, you might have to damage that part of your car beyond repair to do it.

You can break the anti-siphon mesh screen to enter the hose into the fuel-filler opening. However, do this carefully, as the debris from the screen can block fuel flow. Make sure you have the right tools for the job.

Siphoning gas can be dangerous if you don’t do it properly. So before doing it or any other task that involves fuel, consult with a trusted mechanic or read a manual or step-by-step guide. Seep gas out of your tank only when the need is dire.

About The Authors
Reviewed By Richard McCuistian, ASE Certified Master Automobile Technician

Technical Reviewer at CarParts.com

Richard McCuistian has worked for nearly 50 years in the automotive field as a professional technician, an instructor, and a freelance automotive writer for Motor Age, ACtion magazine, Power Stroke Registry, and others. Richard is ASE certified for more than 30 years in 10 categories, including L1 Advanced Engine Performance and Light Vehicle Diesel.

Written By CarParts.com Research Team

Automotive and Tech Writers

The CarParts.com Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by CarParts.com's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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CarParts.com Research Team and Richard McCuistian, ASE Certified Master Automobile Technician