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How Long Does It Take for Gas to Go Bad

How Long Does It Take for Gas to Go Bad

The answer to the question “How long does it take for gas to go bad?” has been much needed as the global crisis of the Coronavirus has hit. Lockdowns after lockdowns have forced people to stay at home. Gone are the daily commutes to work or to school. Cars are now only being used for a quick run to the grocery store. And you just have to wonder what happens to the fuel in these cars if it sits for weeks or even months in the garage? How long does it take for gas to go bad? The answer to that is up to six months, given it is stored properly. 

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Gasoline typically lasts three to six months when properly stored in a labeled, tightly sealed plastic container or metal tank of the capacity recommended by your fire department, but due to oxidation (exposure to oxygen) and evaporation of its volatile compounds, it naturally degrades and loses combustibility over time.


If gasoline is left unused for an extended period of time, it will expire. The issue with gas is that it is highly volatile. A volatile material has a high tendency to separate and vaporize. This is particularly problematic if the fuel vapor has a quick exit from the tank, allowing it to simply evaporate into the air. If this is not the case, the fuel would most likely be considerably less potent than fresh gasoline.


In this article we will discuss gasoline further and what steps you can take to prevent the gas from degrading prematurely.


How Long Does It Take for Gas to Go Bad: Fuel’s Shelf Life


The answer on how long does it take for gas to go bad depends on its shelf life. The amount of time the fuel can stay usable in your gas tank is determined by the type of fuel:



  • Diesel – can last up to a year before degrading


  • Organic-based Ethanol – Will lose its combustibility in as little as 3 months due to oxidation and evaporation.


It can be difficult to keep track of the age of the fuel in your tank. It starts its life in a refinery, where it could have been stored indefinitely before being transported. This time frame could range from a few days to a few weeks. It's likely that the fuel will sit for an extended period of time after it arrives at a gas station, depending on how busy that particular gas station is. It's likely that the gas in your tank was pumped more than a month ago.


How Long Does It Take for Gas to Go Bad: How to tell Your Gas Has Gone Bad


The chemical properties of gasoline change as it ages. As a result, the engine is unable to properly filter the gasoline. If the petrol in your car has gone bad there are a few signs to look for. The most straightforward is your “check engine” light. This light may have been caused by fuel that is burning poorly if the car is running fine and the engine has oil. Investigate your car with a licensed mechanic or a dealership.


If the car has operational issues, this is another sign that the fuel has gone wrong. This could result in a failure to start, a sluggish ignition, a squeaky idle, or a loss of power while driving, especially while accelerating.


When you use old fuel in your vehicle, it can reduce engine strength, causing stalling and hesitation. The worst-case scenario is that your car won't run. Fortunately, if you act quickly, there are a few easy ways to protect your car's oil in the long run. The two most critical steps are to fill up your car's fuel tank fully and to apply a substance called fuel stabilizer.


Greg Brannon, AAA's director of automotive engineering and industry relations, said the most important thing to remember is that gasoline is a living chemical. He said you can tell if you have bad gas by the way it smells when it breaks down. Old gas will start to smell like varnish, will darken, and will have a gumminess to it that good gas does not have.


Brannon also said that at that point the bad gas will start to cause problems with your vehicle’s fuel pump and fuel injectors, so it will affect the vehicle’s performance because the gasoline is no longer behaving the way it should.


Besides causing car performance issues, bad gas can break down and leave residue along the hoses and fittings of the fuel system. Water in the gas, if present, will separate and cause corrosion in the fuel system. In addition to that, it could be difficult to bring old gas out of the tank and get new fuel into the fuel system if the gas has gotten too old to power the engine.


So as mentioned earlier the appearance and smell of gasoline can also be used to assess its condition. The presence of bad fuel would be darker or muddier while the liquid form of gas is usually transparent or slightly yellowed. Besides the varnish smell, it may also have a sour or unpleasant odor that is not typical of regular gasoline. Some people can also think the fuel smells spoiled.


In both of these situations, the bad fuel must be removed from the tank. Not only because the vehicle would not perform as it should, but also because bad gasoline can damage internal engine components and leave a gummy residue that can cause fuel line blockages. Bad fuel, especially Ethanol-containing gas, can draw in water vapor, corroding the tank and fuel system. The harm can be expensive to repair if left unattended for a long time.


How Long Does It Take for Gas to Go Bad: Fuel’s Shelf Life: How to Lengthen Gasoline Shelf Life


Because of the wide fluctuations in diesel fuel prices, especially lately, many people opt to buy in bulk and store the fuel they need for their vehicles on-site, but even this comes at a cost. There are risks associated with unused fuel, but the problem of fuel degradation is much more significant.


There are two issues here. First, since diesel fuel is a carbon-based petrochemical, it begins to oxidize as soon as it leaves the refinery, forming the sediments and gums that clog fuel.


So how long does it take for gas to go bad? Without diesel fuel additives, diesel can go bad in as little as 30 days, causing deposits that can harm fuel injectors, fuel lines, and other system components, reducing fuel efficiency and output. But if you really really must stockpile on fuels, here are some ways to lengthen its shelf life:


  1. The first step is to set aside time to drive your car. This will prevent the fuel from being stagnant, even though it is just for a short distance a few times a week. It would also require you to refill your tank with new fuel every month or two so you do not have to worry how long does it take for gas to go bad.


  1. Water is a significant problem in diesel fuel for many reasons. One is that modern diesel blends often include biodiesel, which has a higher water content by nature. If the water isn't segregated from the gasoline, it can find its way into the fuel injectors. Pressures of up to (40,000) PSI are used in newer common rail fuel systems.


If even a single droplet of water finds its way to the fuel injector from one of the latest high-pressure systems, it may blow the tip-off, which is a costly fix. This slime, like oxidation, can clog the fuel and cause long-term harm. You will reduce the amount of water in your tank by holding it full, which reduces the amount of condensation space in the tank and hence minimizing the amount of water.


The amount of moisture in the tank leads to water pollution and eventual corrosion. A full tank also reduces the amount of oxygen in the tank, which prevents the fuel from evaporating.


  1. A fuel stabilizer, which is an additive that prevents fuel breakdown, is another choice. It's mixed into a full tank of gas to extend the life of the fuel. For many people who drive less these days, this is a smart choice.


  1. Finally, if you plan on storing excess fuel, keep it in an airtight container in a cool, low-humidity, low-oxygen environment. Containers should be between three and five gallons in size. When your stored gas is exposed to high heat and humidity, it becomes more volatile, increasing the risk of fire and explosion. So storing more than five gallons of fuel in a container is not recommended.


  1. Always make a note or label of when the gas was bought and stored so you know which container to take out and use first. Maintain a cool, low-oxygen atmosphere for the gas.


  1. Diesel fuel treatments that demulsify or separate water from the fuel are available for use. A Fuel Water Separator (FWS) filter is used in almost all diesel engines. The performance of the body is improved by demulsification (FWS). All OEM manufacturers suggest demulsifying diesel fuel to ensure that water can be safely removed without causing damage to your engine.


For fuel storage tanks, standard good fuel maintenance practices must be followed. These procedures include the removal of water that has accumulated at the tank's bottom on a regular basis. Since water is heavier than gasoline, it will sink to the bottom, where it will be safer than in your fuel system.


To prevent microbial development, maintenance doses of a dual phase (works in both water and fuel phases) biocide should be applied twice a year. You'll need a diesel fuel stabilizer to prevent oxidation; diesel fuel is very different from gasoline and requires specialized equipment to function properly. Do not use fuel additives that appear to work in both gas and diesel for best results.

How Long Does It Take for Gas to Go Bad: Fuel’s Shelf Life: Tips When Storing Gasoline


People may consider stocking up on spare fuel stored in gas cans in their garage during these uncertain times without really worrying how long does it take for gas to go bad. But there are a few things experts advise against.


Stocking up on gasoline isn't a smart idea unless you plan on using it over the next few months. Adding a fuel stabilizer to the stored gasoline will help, but it isn't a long-term solution. Even with a stabilizer, gasoline will inevitably start to break down at some point.


Stockpiling fuel is not recommended by AAA because it can lead to people getting so much fuel on hand that they can't use it until it spoils. It’s not like you just can pour old gasoline down the drain; it must be properly disposed of at a recycling plant.


If you do decide to store fuel, make sure it's in a DOT-approved, tightly sealed bottle.  Also take note that new, compact gas cans do not have vents like old gas cans. They are sealed to prevent evaporative emissions. This also extends the life of the fuel.


How Long Does It Take for Gas to Go Bad: Fuel’s Shelf Life: Other Frequently Asked Questions

  • Are gas additives worth it?


In addition to cleaning your fuel system, additives will provide your engine with a slew of other advantages. Additives that claim to improve gas mileage are a common commodity, especially as gas prices rise. The Federal Trade Commission's website, on the other hand, advises consumers to be cautious.

  • Can bad gas affect your transmission?


While such delays in starting and engine stalling could indicate expensive transmission and engine repairs, they could also be signs of degraded gas. If you have any issues with your vehicle, take it to a mechanic for a regular check-up and consider switching to a different gas station.


So how long does it take for gas to go bad? As mentioned above, up to 6 months but many factors come into play. The type of fuel, how you store it and how you drive. It can be a tedious process to follow all the guidelines but it might just be worth it most especially during these times.