Gasoline shelf life — How long does gasoline last?

Factors Affecting Gasoline Shelf Life

There’s no set answer because it depends on storage conditions. But you want an answer anyway, right? Ok, when stored properly, gasoline shelf life is 3 to 6 months, according to some experts. Other experts same that ethanol blends start to go bad in as little as 30-days. Who’s right? Both. Read on to learn more about gasoline and what makes it go bad.

The length of time gasoline can safely sit in a gas can depends on several factors, including the type of gas, the storage conditions, and whether any stabilizers are added. Here’s a general breakdown:

1. Regular Gasoline (Unstabilized) Shelf Life: Gasoline shelf life 3 to 6 months— Gasoline can start to degrade after about 3 months if it is stored in a typical plastic gas can without stabilizers. The degradation process involves the gas oxidizing and absorbing moisture, which can lead to the formation of gum and varnish deposits, reducing the fuel’s effectiveness and potentially causing damage to engines.

2. Gasoline with Stabilizer Gasoline Shelf  Life: 12 months to 2 years— If a fuel stabilizer is added to the gasoline, it can extend the shelf life significantly, often up to a year or more. Stabilizers prevent oxidation and moisture absorption, allowing the gas to remain usable for a longer period. However, it’s important to note that stabilizers work best if added to fresh gasoline, not gas that has already started to degrade.

3. Ethanol-Blended Gasoline (E10, E15, etc.) Shelf Life: 1 to 3 months— Ethanol-blended fuels have a shorter shelf life compared to pure gasoline. Ethanol is hygroscopic, meaning it absorbs moisture from the air, which can lead to phase separation where water and ethanol settle at the bottom of the tank or can. This process can start to occur within a month or two, especially in humid conditions.

4. Storage Conditions: Temperature— Gasoline stored in a cool, dry place with stable temperatures will last longer than gas stored in fluctuating temperatures, especially in areas with high heat.

Container: Metal gas cans or high-quality plastic cans with tight-sealing caps are better at preventing air and moisture from entering, thereby extending the life of the gas.

5. Signs of Bad Gasoline

Odor: Gasoline that has gone bad often has a sour or varnish-like smell.
Color: Fresh gasoline is typically clear or light amber. If it appears dark or murky, it may have started to degrade.
Performance: If used in an engine, bad gasoline can cause starting problems, poor engine performance, or even damage to the fuel system.

What makes gasoline go bad?

There is no such thing as pure gasoline. Gasoline is a blend of up to 150 different components, and it’s formulated differently by every local/regional refiner to meet the needs of the local community where it’ll be used. The refiner varies the components and proportions based on the season (summer gas versus winter gas), altitude, and raw material prices. But all gasoline has one thing in common, it must vaporize quickly and ignite and burn in a controlled manner.

The volatile components in gasoline make it vaporize and burn, and those same volatile components can affect gasoline’s shelf life if it’s not stored properly. So let’s take a look at what ages gasoline.

Air makes gasoline’s volatile components evaporate out of the mixture

Exposure to air is the #1 cause of reducing gasoline shelf life. Air exposure causes the volatile components in the gasoline to evaporate and leave the remaining mixture less able to vaporize and ignite.

Air makes the remaining components oxidize and turn to gum and varnish

Leave a glass of wine out on the counter for a week and see what’s left. The alcohol will be gone, and the wine will be thick and gooey. The same thing happens to gasoline. As the volatile components evaporate, the remaining components oxidize, causing gum and varnish deposits that can clog the small passages in carburetors and fuel injectors.

Moisture in the air combines with the alcohol to reduce gasoline shelf life

Ethanol blends contain alcohol, and alcohol is hygroscopic (it absorbs moisture from the air). If the gasoline is stored in a vented gas tank, like on a small engine, it will absorb moisture in the air. After about 30 days in humid conditions, the ethanol blend will go through PHASE SEPARATION, where the alcohol/water will separate from the gasoline and fall to the bottom of the tank. From that point on, the engine will be supplied with the alcohol/water combination.

The storage container—plastic versus metal gas cans

Many gasoline storage containers are made from plastic, mainly polypropylene/polyethylene. Those containers allow some of the highly volatile components to pass through the plastic and evaporate. Metal gas cans don’t allow that passage, so gas stored in metal gas cans tends to increase gasoline shelf life.

Gasoline shelf life is shorten when it’s stored in plastic gas cans as opposed to metal gas cans

What is a gas stabilizer?

Gas stabilizers contain chemicals that slow down phase separation and prevent gum and varnish formation. In addition, some fuel stabilizers contain a metal-deactivator ingredient that prevents metal oxidation in carburetors, fuel pumps, and fuel injectors.

When to add gas stabilizer

Add a gas stabilizer at the pump when filling your gas can. That way, it will be fully mixed with fresh gasoline and protect the gas right from the get-go.

How long does a gas stabilizer last?

Some gas stabilizer manufacturers claim that gasoline stabilized with their product extends the gasoline shelf life up to three years.

Can you add a gas stabilizer to the old gas?

You can, but it won’t do any good. Dead gasoline is dead. You can’t bring it back to life because all the volatile components are already gone and the rest of the gas has already turned to gum and varnish.

©, 2020 Rick Muscoplat