How to Get Rid of Bad Gas in a Car

by Lisa ParrisUpdated June 12, 2023
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Refuelling by gasoline of the modern car image by terex from

Cars need gasoline to run properly. However, even on a full tank, drivers can experience difficulties. The engine not starting, lack of engine power, or engines that sputter and run on--these are all signs of bad gasoline. Once the bad gasoline is in the tank, it either has to come back out, or it must be “fixed” in some way. Ignoring bad gas can lead to clogging, stalling, weak engine power and irregular combustion.

Things You'll Need

  • Garden hose
  • Gas can
  • Dry gasoline
  • High-octane gasoline
  • Octane booster

1. Remove the tank and get rid of the bad gas

Remove the tank and get rid of the bad gas. This is the most effective way to get rid of gasoline without harming the engine of the car. However, it is also the most labor intensive and complicated. If you are not a trained mechanic, it may be best to hire someone to do this for you.

2. Siphon the gas out of the tank

Siphon the gas out of the tank. Place one end of a garden hose into the gas tank. Set the other end in an empty gas can. Be sure the gas can is placed lower than the gas tank. Remove the hose from the gas can and gently suck on the end. Return the hose to the gas can as soon as you feel the gas running through the hose. Gravity will move the gas from the tank into the gas can.

3. Add dry gasoline to the tank

Add dry gasoline to the tank. Available in auto parts stores, dry gasoline is designed to absorb water without affecting the performance of the engine. Water is one of the most common gasoline contaminants. When pumped into a gas tank, it sinks to the bottom and is immediately forced into the engine. Since water won't combust, it causes the engine to pop and sputter.

4. Fill the tank with high-octane gas

Fill the tank with high-octane gas and then add an octane booster. Repeat two to three times, adding gas every time the gas gauge falls below half a tank. This method will dilute the bad gas by mixing it with good, enabling the engine to run properly until the bad gas is gone.


Do not add rubbing alcohol to the gas tank. Isopropyl alcohol is a dilute mixture, meaning it contains water. Adding water to the gas tank only aggravates the problem.

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