If it has been a while since your car has been driven, you may wonder: does gasoline go bad if left unused for a period of time?
The short answer is yes, over time, gasoline can go bad, which leads to a number of problems, ranging from hard starting to rough running to no starting at all.
For some drivers, working from home has meant doing very little driving. However, if you’re planning to keep a vehicle parked and undriven for a long time, letting gas sit in your car’s tank for too long isn’t a good idea.
Gas naturally degrades and loses combustibility over time and leaves deposits or gums, particularly in sensitive areas like injectors or jets. Once gas loses its engine-igniting ability, it could damage fuel system components.
Another issue is the accumulation of water in the tank if there is space inside it to collect condensation, but it also depends on the humidity where the gas is stored.
While gasoline can likely be kept for months to years, environmental factors such as heat, oxygen, and humidity influence the fuel’s condition.
Different types of fuel have different lifespans. Ethanol-blended gas lasts up to three months. According to the U.S. Energy Information Administration, most gasoline sold in the U.S. is “E10” gas made of 90 percent petroleum-based gas and 10 percent ethanol (ethyl alcohol).
Ethanol-blended gas usually has a shelf life of up to three months because of the high speed at which ethanol oxidizes.
The higher the ethanol content in the gas, the shorter its shelf life, so E15 (15 percent ethanol content), E20 (20 percent ethanol), or E85 (85 percent ethanol) gas will expire sooner than E10 gas will.
Compared to Ethanol-blended gas, pure gasoline can be kept for at least six months.
Petroleum-based gasoline without any ethanol will still succumb to oxidation and volatile compound evaporation in a sealed container or tank but more slowly. In pure gasoline, you can usually expect it to last at least six months when properly stored.
Diesel fuel can last twice as long, around six to twelve months. The reason these numbers are so broad is that it’s hard to tell how old the gas actually is.
It may have been sitting inside the gas pump for a month already before you came to fuel up. You also don’t know how long the gas was stored at the refinery before it was transported to the gas station.
You’ll be able to tell if your gas is going bad just by starting your car. If it has a rough idle, stalls frequently during acceleration, or fails to start at all, your gas has gone bad. Sometimes, bad gasoline will also cause the check engine light to illuminate.
You can also tell if gasoline is bad by its appearance. Oxidized fuel often turns darker over time and may even smell sour. You can check stored gasoline by pouring some into a clear glass container and comparing it side-by-side with known fresh gasoline.
If your old sample looks noticeably darker than the fresh gas, you have strong evidence the gas has gone bad.
You should also avoid topping off your tank, which can damage the tank’s vapor recovery system.
Get to know the gas station’s peak activity times, so that you can avoid crowds of cars.
The result is diminished engine performance. Your engine may still start and run, but it probably won’t run as well. Fortunately, a new gas cap is a quick and inexpensive fix.
Fill the gas tank three-quarters of the way with fresh gas, top it off with old gas, and then try starting the car. The good news: Once the old gas has been consumed and the tank is topped off with fresh fuel, the problem should cure itself.
Depending on the product, the stabilizer can increase gasoline shelf life to between one and three years. Using fuel system stabilizer for extended storage is preferable to draining the tank and leaving the system dry.
This can cause rubber hoses, gaskets and seals to dry-rot and crack, possibly leading to leaks and even a fire.
In addition, a dry system can expose the insides of metal fuel lines and your gas tank to air and moisture, which can lead to or accelerate the formation of rust.
Fuel system stabilizer is not a cure-all, and it doesn’t last forever. Stabilizers work best when you mix them with new gasoline; they’re ineffective at slowing the degradation of old gas, and they can’t return contaminated gas to working order.
Never dispose of gasoline in trash cans, drains, sewers, lakes or streams, or on the ground—it’s highly flammable and can contaminate local water sources.
Dispose of contaminated gasoline at the earliest opportunity because both the gas and the vapors it emits are still flammable and could cause a fire or explosion if the storage container were to become damaged over time, and the gas were to leak into its surroundings.
To safely dispose of old or contaminated gas, contact your city waste or fire department for the approved disposal gasoline site.
Generally, it’s best to be cautious and use all the gas in your tank before a few months have passed. When gasoline goes bad, it won’t burn correctly inside the engine. It could also be exposed to water contamination, which may lead to corrosion in the fuel system.
It makes sense to spend the time to totally drain the fuel system. It’s cheaper than replacing the fuel system, later on, due to dried up, gummy gas deposits.
Always consult a mechanic on how to best remove or fix gas going bad in a car. Consult American Auto Care for this and other auto concerns. We care about ou and our car.
We are always happy to answer any questions. Call us at 951-461-2507.