The Seasoned Wrench


Will Bad Gas Cause A Misfire? Yes, and No [Find Out]

Chase Manhattan Avatar

Last Updated:

Note: My posts may contain affiliate links. If you click on these links and make a purchase, I may receive a small commission at no extra cost to you. I only recommend products I genuinely believe in. Thanks for supporting The Seasoned Wrench!

Read my full affiliate disclaimer >>

Having a reliable vehicle is essential in our daily lives — it gets us from point A to point B, often without a hitch. But, there are instances when our vehicle might not function as expected, like experiencing an engine misfire. One question that often arises in car owners’ minds is, does bad gas cause misfires?

The simple answer is yes, bad gas can cause a misfire. But it’s not the only reason, and the situation is a little more complex than it initially appears. In this article, we will explore the relationship between bad gas and engine misfires, examine other potential causes of misfires, and discuss how to identify and rectify the issue of bad gas.

Why Does Bad Gas Cause Misfires?

Understanding why bad gas can cause a misfire requires a little knowledge about how your car’s engine works. When everything is running smoothly, your vehicle’s fuel injectors spray a precise amount of gasoline into each cylinder. This gasoline is then ignited by the spark plugs, causing a small explosion that pushes the cylinder down and turns the engine.

Bad gas can disrupt this process in a few different ways:

  • If the gas is old or was stored improperly, it might have lost its potency, causing it to ignite inconsistently or not at all.
  • Contaminated gas can lead to clogged fuel injectors, which disrupts the spray pattern and amount of gas delivered into the cylinder.
  • Gas with the wrong octane rating can ignite at the wrong time, which can cause a misfire.

So, while it’s not the most common cause of misfires, bad gas can certainly play a role.

Related article: Breather Bypass Procedure

What Else Causes Misfires?

As mentioned above, several factors can cause an engine misfire beyond just bad gasoline. Let’s dive a little deeper into these potential culprits:

  • Faulty Spark Plugs: Spark plugs are crucial to the combustion process, igniting the fuel-air mixture in the cylinders. If a spark plug is faulty or worn out, it won’t be able to properly ignite this mixture, leading to a misfire.
  • Broken Coil Packs: Coil packs are responsible for converting the low voltage electricity from your car’s battery into the high voltage electricity needed to spark the spark plugs. If a coil pack is broken, it won’t be able to provide this necessary voltage, resulting in a misfire.
  • Blocked Catalytic Converters: Catalytic converters are part of your car’s exhaust system, helping to reduce harmful emissions. If a catalytic converter is blocked, it can cause an increase in back pressure in the exhaust system, which can lead to misfires.
  • Electronic Sensor Failures: Modern vehicles rely on a variety of electronic sensors to monitor and control different aspects of the engine’s operation. If one of these sensors fails, it can throw off the engine’s timing or fuel-to-air mixture, leading to a misfire.
  • Leaking Head Gaskets: Head gaskets seal the gap between the engine block and the cylinder head, preventing coolant or oil from leaking into the cylinders. If a head gasket is leaking, it can cause coolant or oil to enter the cylinder, which can cause a misfire.

If your vehicle is experiencing consistent misfires, it’s important to have it inspected by a skilled mechanic who can diagnose and repair the issue.

Keep reading: Bad Stator Symptoms

How To Identify Bad Gas

Identifying bad gas can be a little tricky, as the symptoms can be similar to other issues with your vehicle. However, there are a few signs you can look out for:

  • Poor Performance: If your vehicle is running poorly, struggling to accelerate, or experiencing a decrease in fuel efficiency, it could be due to bad gas.
  • Engine Misfires or Stalls: As we’ve discussed, bad gas can cause your engine to misfire or stall, or not start at all.
  • Strange Noises: Bad gas can cause your engine to make unusual noises, such as knocking or sputtering sounds.
  • Check Engine Light: In some cases, bad gas can cause your check engine light to come on.

If you suspect you might have bad gas, the best course of action is to have your vehicle inspected by a professional. They can test your fuel and diagnose any potential issues.

Here’s a video describing how you can identify bad gas in your car:

What To Do About Bad Gas (How To Fix)

If you suspect that bad gas is causing issues with your vehicle, there are a few steps you can take to remedy the problem:

  1. Drain and Replace the Fuel: If you have a significant amount of bad gas in your tank, it may be necessary to drain the tank and replace the fuel. This should be done by a professional, as improperly handling gasoline can be dangerous.
  2. Use a Fuel Additive: There are various fuel additives available that can help to clean out your fuel system and remove any contaminants. These can be a good option if you have a small amount of bad gas in your tank.
  3. Check and Replace Fuel Filters: Bad gas can clog your fuel filters, so it’s a good idea to check these and replace them if necessary.
  4. Inspect and Clean Fuel Injectors: As mentioned earlier, bad gas can cause your fuel injectors to become clogged or dirty. Have these inspected and cleaned if needed.
  5. Visit a Mechanic: If you’re not comfortable doing these steps yourself, or if the problem persists after trying these solutions, it’s a good idea to visit a mechanic. They can diagnose and fix the issue for you.

How Do You Wind Up With Bad Gas?

Bad gas can occur for a few different reasons:

  • Poor Storage Conditions: Gasoline should be stored in airtight containers and kept in a cool, dark, dry place. Exposure to heat, light, or moisture can cause the gas to degrade and become “bad.”
  • Old Gas: Gasoline doesn’t have an indefinite shelf life. Over time, it can lose its potency and become “bad.” Generally, gas should be used within a few months of being purchased.
  • Contaminated Gas: If dirt, water, or other contaminants get into the gas, it can cause it to become “bad.” This can happen if the gas is not stored properly, or if it’s contaminated at the pump.
  • Incorrect Octane Rating: Using gas with an incorrect octane rating for your vehicle can also cause issues. Be sure to use the correct type of gas for your vehicle to prevent this.


Related: Motorcycle Popping on Deceleration? Know This (2023)

Here’s a table giving you an example of the degradation timeframe for gasoline:

Storage ConditionDegradation Time
Sealed Container (No Air Exposure)6 months to 1 year
Open Container (Some Air Exposure)3 months to 6 months
Hot Temperature (Above 85°F/30°C)1 to 3 months
Cold Temperature (Below 32°F/0°C)6 months to 1 year
Contaminated (Water, Dirt, etc.)Accelerated degradation varies

Related Questions

In addition to the main topic of whether bad gas can cause a misfire, there are a few related questions that often come up. Here are two of the most common ones:

While a single misfire is unlikely to cause permanent damage to your engine, consistent or severe misfires can lead to significant damage. If your vehicle is consistently misfiring, it’s important to have it inspected and repaired as soon as possible.

What does a misfire feel like?

A misfire can be felt as a jerk, stutter, or “miss” in the vehicle’s performance. It can also cause the vehicle to shake or vibrate, and it can lead to a decrease in power and acceleration.

How can I prevent bad gas?

To prevent bad gas, it’s important to store it properly (in an airtight container in a cool, dark, dry place), use it within a few months of purchase, and avoid contamination. Also, be sure to use the correct octane rating for your vehicle.

Wrapping Up

To wrap things up, while bad gas can cause a misfire, it’s not the most common cause. If your vehicle is consistently misfiring, it’s important to have it inspected by a mechanic to diagnose and repair the issue.