What is the shelf life of e85?

E85 gas, or flex-fuel, is an ethanol blend that the federal government has been pushing as a viable alternative to gasoline. According to government scientists, ethanol is a much promising source of fuel than gas. Since its production is in large quantities, the process of harvesting it requires little technological interference. However, e85 gas is only compatible with flex-fuel vehicles (FFVs). Filling a non-FFV with e85 gas is extremely dangerous for your fuel system components as well as your engine.  What is the shelf life of e85?

How long does e85 gas last?

E85 gas has a maximum shelf life of one year. Compared to gasoline, ethanol blends have a more stable chemical structure, if stored in proper conditions. At room temperature, it does not decompose or oxidize, unlike gas, which will readily oxidize.

1 year shelf life

However, if you fill your stored vehicle with e85 gas, you have to ensure it is neither too hot nor too cold. Ethanol quickly absorbs water. In low temperatures, the mixture of water and ethanol forms an acidic blend that corrodes your fuel tank as well as other components.

On the other hand, once the ethanol absorbs a substantial amount of water, it separates itself and settles at the bottom of the fuel tank. This causes your vehicle to stall, if you do not remove and replace such fuel.

Proper storage of e85 gas involves consistently maintaining the room temperature and storing it in a fully sealed, dark container. It is best to fill up the storage container to minimize the chances of oxygen reacting with the gas.

Similarly, you may also opt to add ethanol blend additives to fresh e85 gas, such as K100, to eliminate the water, stabilize the fuel, and clean fuel system components as well as your engine.

How do you know if e85 gas has gone bad?

Vehicles move from one place to another as a result of a complex combustion process. The process heavily relies on high-quality gas vapors delivered to the engine’s combustion chamber.

However, if the fuel does not decompose properly to release its fumes, the ignition process is interrupted. This causes the vehicle not to start up properly and leads to poor engine performance.

Water in your fuel tank

When a vehicle is in storage, e85 gas goes bad when it mixes with oxygen during humid conditions and hot temperatures. E85 gas is a mixture of various chemical substances, each with their unique characteristics.

Over a long duration of inactivity, some of these chemical substances decompose or evaporate due to certain environmental factors, causing the gas to go bad. Ethanol is also known to be hydrophilic, meaning it attracts water.

Water in your fuel tank and the engine is hazardous, as it increases the volatility of the gas and increases the chances of rust formation and corrosion.

Stale gas is easily noticeable because of several factors. From color change to odors to texture to stratification, the signs are endless. Pour some of your stored e85 gas into a container and compare it to its fresh equivalent. Fresh e85 gas is clear in color.

Oxidized gas changes to a darker color and has a strong sour smell. You may also notice phase separation, whereby the alcohol (ethanol) separates from the gas. You can even notice stale gas in your vehicle when it experiences difficulty in starting up or stutters, produces ‘pinging’ sounds, stalls, and roughly idles.

Can old e85 gas be restored?

If not stored properly, all fuel has a limited storage life. Due to various environmental factors, chemical reactions in the fuel will degrade its quality and performance. When it comes to dealing with old e85 gas, many car owners ask themselves if restoration is possible.

Many at times, it is not likely for the restoration of old gas, simply because you cannot reverse chemical reactions. It is advisable to add fuel stabilizer though, but only to prevent further gas degradation from occurring.

However, if you find your e85 gas has not undergone phase separation but is darker in color, you may add fuel stabilizer with a high level of detergency.

As a result, as the old e85 gas is burning in your engine, specific components, which do not fully combust, form, leaving deposits in the engine’s combustion chamber. Adding this additive removes such elements as they are formed, ensuring optimum engine performance.


If you choose to purchase a flex-fuel vehicle, or you already have one, it is adamant that you educate yourself on ethanol fuels. However, you will be happy to know that it is possible to store ethanol blends for continuous long durations, without it going bad.

Furthermore, you can also restore old e85 gas if it has not phase-separated. If you often leave your vehicle parked in your garage for long periods, you may consider tuning up your car to enjoy the long shelf life of e85 gas.

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