How long is gas good for sitting in a gas can?

Gasoline has a shelf life and will eventually go bad if left unused for too long. How long gasoline lasts depends on a variety of factors, including the type of gas, the gas can and how it’s stored. Here’s what you need to know about how long gas stays good in a gas can.

How Long Does Gas Last in a Gas Can?

In general, gas tends to last 3-6 months in a sealed gas can if stored properly. However, gas can start to degrade and go bad in as little as 30 days if it’s contaminated with water, dirt or other impurities.

Here are some general guidelines for how long gas lasts in a gas can:

  • 1-3 months – Gas is still fresh but may start to evaporate or lose volatility.
  • 3-6 months – Gas is reaching the end of its shelf life, may suffer from decreased combustibility.
  • 6-12 months – Gas is expired, may be unusable in engines due to oxidation and lack of volatility.

Note that these timeframes assume the gas has been stored properly in an airtight, approved gas can. Gas that is stored for longer than 3-6 months may suffer from decreased performance, but is not necessarily unusable.

What Factors Affect How Long Gas Lasts?

There are several key factors that impact how long gasoline stays fresh and combustible when stored in a gas can:

  • Gas blend – Standard 87 octane gasoline lasts 2-4 months, while premium grades with detergent additives can last 4-6 months.
  • Ethanol content – Ethanol absorbs water and can cause gas to go bad quicker. E0 and E10 gas lasts longer than E15 or E85.
  • Outdoor temperature – Hot weather causes fuel to evaporate and degrade faster. Gas lasts longer when stored in a cool, dry place.
  • Storage container – Approved gas cans with tight seals prevent air and water from getting in to contaminate fuel.
  • Exposure to air – Oxygen causes gas to oxidize and degrade over time. Minimize air in the container.

Storing gasoline properly is key to maximizing its shelf life. Keeping gas cool, dry, and sealed in an airtight container can extend its lifespan to 6 months or longer.

Signs Your Gas is Going Bad

Here are some signs that the gasoline in your gas can may be going bad and reaching the end of its usable life:

  • Change in color – Fresh gas is clear or light yellow. As it ages, it can turn a darker yellow/orange.
  • Cloudiness or haziness – Particles and impurities in old gas make it look hazy.
  • Thick, sludgy texture – Gum, varnish and sediments form over time.
  • Strong odor – Gas gives off stronger chemical fumes as it oxidizes.
  • Engine problems – Hard starting, stalling, or engine knock point to fuel issues.

If your stored gas shows changes in appearance, texture or smell, it may be too old to use – especially in small engines. The easiest way to test old gas is to add it to your car’s tank in small amounts. If it causes issues, it’s time to dispose of the old gas.

Does Gas Go Bad in a Gas Can?

Yes, gas absolutely can go bad when left sitting in a gas can for an extended period of time. While gasoline itself does not technically “expire,” it does start to degrade through oxidation and evaporation after just 1-6 months of storage.

The compounds in gasoline – hydrocarbons, alcohol, additives – are volatile and reactive. Gas reacts with oxygen, water, light, and the inside of the container, changing its makeup over time. Compounds evaporate, sediment forms, and the gas becomes less potent and effective.

Any gas stored for more than 3-6 months should be inspected carefully and tested before use. Old gas may damage engine components if used in lawn mowers, chainsaws, boats, ATVs or other equipment after it has gone bad.

How to Store Gas to Increase Shelf Life

Proper gas storage is crucial to maintain its quality and extend shelf life. Here are tips for storing gas correctly:

  • Use an approved gas storage can made of steel or polyethylene plastic.
  • Fill the can 95% full to minimize air space and evaporation.
  • Add a fuel stabilizer like Sta-Bil to prevent oxidation.
  • Keep in a cool, dry place away from direct sunlight.
  • Store at temperatures between 40°-70°F to maintain volatility.
  • Place on a raised surface off concrete to avoid moisture and rust.
  • Seal tightly after each use to prevent vapors escaping.
  • Label with type of gas and date filled.
  • Use older gas first before fresher fuel.

Following gas storage best practices helps maintain the quality and longevity of your stored fuel.

How to Dispose of Old Gas

If your gas shows signs of aging, it’s time to properly dispose of it. Here are safe methods to get rid of old gas:

  • Use in a vehicle built for lower-quality fuel, if performance allows.
  • Mix with fresh gas in proper ratios to dilute.
  • Add to your car’s tank in small amounts (25% or less of tank volume).
  • Pour into approved gas disposal containers.
  • Bring to a household hazardous waste collection center.
  • Contact hazardous waste removal companies for disposal.

Avoid pouring directly on the ground, down storm drains or into groundwater. Check local environmental regulations for proper gas disposal methods in your area.

Can You Improve or Fix Old Gas?

There are a few methods that may help rejuvenate old gas and extend its usability:

  • Add fresh gas – Mixing fresh gasoline restores volatility and combustibility. Use in a 5:1 or 10:1 ratio of new to old.
  • Use fuel stabilizer – Additives help treat oxidation and moisture buildup issues.
  • Use fuel injector cleaner – Detergents may dissolve gum and varnish deposits.
  • Filter the gas – Removing sediments can improve performance.

However, there is a limit to how much old gas can be salvaged. If more than 6-12 months old, gas may be too far degraded for additives and mixing to make it usable again.

Frequently Asked Questions

Does gas expire?

Gasoline itself does not have a specific “expiration date.” However, gas does degrade over time due to oxidation, evaporation, condensation, and chemical breakdown. Performance and combustibility suffer after 1-6 months.

Can old gas damage a car engine?

Using very old or bad gas can damage a car’s fuel system and engine. Sediments can clog filters, bad gas does not ignite properly, and corrosion can occur from oxidation byproducts. Adding large amounts of old gas to a car should be avoided.

Can you use expired gas in a lawn mower?

Lawn mower engines are generally more sensitive than car engines. Using gas older than 3-6 months in lawn mowers is not recommended. Small engines are more prone to clogs, abnormal combustion, and deposits from stale fuel.

Does gas go bad in a motorcycle?

Yes, gas can go bad in a motorcycle over time. Always use fresh gas if a motorcycle has been sitting for winter. Drain gas under 3 months old before it degrades. Add fuel stabilizer to extend gas life to 6 months in an unused motorcycle.

How long does diesel last in a tank?

Diesel fuel stored correctly can last 12 months or longer before going bad. Key factors include clean storage tanks, treating fuel for microbial growth, maintaining cool stable temperatures, and adding biocides and stabilizers.

The Bottom Line

Gasoline has a limited shelf life and can go bad in as little as a month if stored improperly. Maintaining a full, sealed gas can, keeping fuel cool and dry, and adding stabilizers extends gas life to 3-6 months. Check for signs of bad gas and dispose of or rejuvenate degraded fuel.

With proper storage and care, gas can last up to a year before oxidation and evaporation take their toll. But remember, very old gas can damage engines and fuel systems. Always monitor stored gas and stick to a first-in, first-out use strategy.

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