How To Dispose Of Old Gas Mix

hand in a glove pours gasoline into a tank of a red lawn mower, closeup view

I pulled the weedeater gas can out of the garage to go get fresh gas. Unfortunately, it had sat all winter and now the gas mix was congealed and bad.

In the past, my dad would always pour the old gas mix on grass that we wanted to kill. Disposing of old gas became an impromptu weedkilling session.

My grandfather had a different use for old gas oil mix. He would use it as fire starter on the many burn piles dotting his farm.

You probably have a similar upbringing. Instead of encouraging EPA violations, I wanted to present the right method for handling old gasoline.

Here is what this article will cover:

See Related: Compressor Vs Motor Oil

How Long Does Gasoline Last?

Gas Oil Mix is good for 3 to 6 months. The new Ethanol blends that most American gas stations sell only last for about 3 months.

According to the US Energy Information Administration, most gasoline in the US contains 10 percent ethanol. The higher the level of ethanol, the faster the gasoline will degrade. E20 (20 percent ethanol) will degrade faster than the standard E10 gasoline.

The organic-based ethanol is more likely to oxidize from the surrounding air, losing its ability to combust.

The fuel you buy at your local gas station might be a month old by the time you buy it. Fuel must leave the refinery where it was made, truck across the country, and be stored in an underground tank at your local gas station.

How To Identify Bad Gasoline

Old gasoline is no longer has the properties that allow it to be burned well by a vehicle. To understand this, we need to first discuss how combustion works. Combustion works when highly flammable material is exposed to oxygen and heat.

In your lawnmower or weedeater, the gas oil mix is sprayed as a fine mist. The spark plug then fires, igniting the gasoline as it rapidly combines with the oxygen in the surrounding air.

Bad gasoline has degraded by slowly binding with free oxygen in the surrounding air. It also draws water in, mixing with the oxygen found in water. While still being flammable, it is no longer as flammable as needed for a good clean burn and can damage the fuel system.

You can identify old gasoline by its appearance. Bad fuel will be darker than fresh gas. It will also not smell as pungent as new gas does. Since old Gas oil mixtures are already darker from the added oil, you will need to determine it’s viability based on how old it is.

When stored in a tank, gas mix will draw in water from the air and can speed the rusting of the gas tank and damage seals in the carburetor.

Running old gas oil mix through a lawnmower, generator or weedeater can coat the tiny ports in varnish and degrade seals, causing a long term decrease in power.

It is important to drain old gas oil mix from your fuel tank before the season ends. On weedeater, you just use a funnel and flip the fuel tank over to pour it out.

If you are storing a vehicle, you should also drain the fuel. Even if you have a lifted truck with lots of space underneath of it, this will generally involve dropping the tank, or siphoning the old fuel from the tank.

How To Keep Gas Fresh

On generators and other equipment that may sit for long periods of time, gas can be made to last for up to a year with the addition of a fuel stabilizer.

Fuel stabilizer must be added in the ratio of one ounce per 5 gallons of fuel. Add the stabilizer first, and then add the fuel. This will keep the gasoline fresh for up to one year.

Storing Gasoline Safely

I am always amazed at how unsafely gasoline is stored and transported.

There are a few basic rules that need to be followed when storing gasoline.

  1. Store mixed fuel at least 50 feet away from an open flame source such as a heater, pilot light on a hot water tank or pilot light on a stove. Fumes can travel and ignite, so an adequate distance needs to be maintained.
  2. Store out of the reach of children.
  3. Ensure the lid tightly seals shut when not in use.
  4. Store in a structure separate from the main residence.
  5. Do not store gasoline where the temperatures will exceed 100 degrees. A hot summer day in a shed can be too warm for gasoline. If stored in a shed, additional ventilation can control summer temperatures in the space.
  6. Do not store directly on concrete as that can increase the absorption of water. Put a layer of wood or cardboard underneath it.
  7. Do not store in direct sunlight.

How To Properly Dispose Of Gas Oil Mix

It is quite easy to dispose of old gas and depending on your location, it may be free. Some auto parts shops may accept it like they do with waste oil, however, since gas is more flammable, most auto parts stores will decline to receive it.

Here are the steps to properly dispose of old gas.

  1. Put the gasoline in an approved container. Generally the original container is preferred, but glass can also be used to hold gasoline. Every container should be clearly labelled.
  2. Search Google for an approved chemical waste disposal facility. These are generally run by your local government.
  3. Transport to the facility using a vehicle with plenty of ventilation.

Once at an approved waste management company, they will process it in accordance with EPA regulations. Generally, there is a limit on how much quantity can be dropped off in a single visit.

Gas oil waste removal must be done properly to protect yourself, your equipment and the environment. Safely dispose of the old gas oil mix using the above 3 steps.

Image of a Chemical Waste Recycling Center

How To Start An Engine With Old Gas Oil Mix

The best solution is to remove the old fuel and add new. However, there are several options for rejuvenating the old gas. (Thankfully, the oil tends to hold its lubricating properties). If your small engine has a small carburetor with a float bowl, be sure to remove the float bowl and drain the old gas oil mix out before trying to start it.

Fresh Gas

Old gas mix can be used in a 1:5 mixture with fresh gas. For every gallon of old gas, add 5 gallons of new gasoline to dilute it.

High Octane Additives

High octane boosters can be added to restore the flammability of gasoline and dry it out. 5 ounces of octane booster can restore up to 21 gallons of gasoline. Be aware that high-ethanol boosters can be hard on the seals in your small engines.

Filter and Settle

For best results, filter the old gas through a coffee filter and then let it sit in a glass container. In the next hour, the water will settle out of the bottom of the gasoline, making it possible to pour the less saturated gas off of the top. With a little octane booster, this old gas oil mix is nearly as good as new.

Storing Your Small Engine For Winter

The key thing is to empty the fuel. Put it into an approved container and dispose of the old gas oil mix properly using the steps above.

In addition to removing the fuel from the tank, also drain the carburetor bowl of any remaining fuel mixture.

Is 2-Year-Old Gasoline Still Good?

Two-month-old gasoline is still good enough to use. However 2-year old gasoline is too old to safely use without a decrease in engine performance. Gasoline that is older than three months can cause engine knocking and even no-start conditions.


Zachary Drumm

Hey! My name is Zachary Drumm! This site allows me to test new tools, piddle around in the garage, and share the insights I get from flipping cars and houses. When it comes to tools, home improvement, and being a “shade tree mechanic,” you’ve come to the right spot. If I’m not in the garage creating content, you’ll find me outside, running, canoeing, and traveling. My goal is to empower more people to be self-sufficient.