You go to start your engine without success, remembering that it’s been a long time since any gas passed through the engine. You think to yourself, is it possible for gas to go bad if it’s been sitting for an extended period?

If you have been in a similar situation and would like to prevent this from happening in the future, here’s what you need to know about the properties of gasoline.

Can Gas Actually Go Bad?

Many people are surprised that gas can go bad, not realizing that it can until it’s too late. Although gasoline will likely keep for months, there are a number of environmental variables that impact its condition. From oxygen to humidity, if you leave gas untouched for an extended period of time, it simply won’t perform as well and it could even damage your engine.

The main issue in regards to bad gas is what’s known as phase separation. This is becoming increasingly common as the use of ethanol continues to rise. This occurs when water gets into the gas, allowing ethanol to bond to the molecules. Since petroleum does not blend with water, water separation will occur, resulting in a lower octane number — which is essentially a standard measure of performance. The lower the octane number, the greater the chances are that the engine knocking will result.

The problem is, ethanol naturally attracts water, absorbing humidity from the air outside the tank it’s stored in. When this happens, two main layers begin to form — a gas-only layer which settles on the top, in addition to a milky water-ethanol blend on the bottom. There is also often a very thin layer of water at the very bottom. This is why it’s recommended that you store your gasoline in a cool, low-oxygen environment.

Whether you are trying to start up your car, lawn mower, or boat, if the gas has separated, the engine and the equipment itself won’t perform. You will also run the risk of corrosion in the fuel system, or your equipment may sustain other types of damage.

How Long Does Gas Last and What Can I Do to Enhance Its Efficiency?

Although there are a number of factors to consider, when it comes to the longevity of E10 (gas that contains 10 percent volume of ethanol), a general rule of thumb is around 90 days. However, this is only when the gas is stored under the right conditions. For example, the external temperature can have a significant impact on the amount of water that ethanol can hold.

In order to protect your gasoline during storage, you should source an ethanol treatment, such as STA-BIL 360°® Protection™. Now only will your gas keep longer, staying fresh for up to 12 months, but it will also effectively clean the fuel system in the process. In turn, this prevents corrosion and the need to drain your fuel system in order to clean it.

What Should I Do If My Engine Won’t Start?

If you have not been storing or maintaining your gasoline in a proactive manner, you can still often intervene. Although you cannot bring bad gas “back to life” — you can often kickstart a fuel system following extended storage. Whether you are trying to start up a 2- or 4-cycle engine, STA-BIL® Start Your Engines! is both easy-to-use and most importantly, effective.

Categories: Fuel Tips


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