How to Rejuvenate and Recondition Old Gasoline

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You carefully stored away gallons of gasoline, ready for whatever eventualities the world might throw at you. Now, six months later, all that gasoline is busy degrading, losing its potency and combustibility. 

Not only does old gasoline burn less efficiently, but it can also destroy engines, causing blockages and internal corrosion. 

Fortunately, there’s a simple method for making old gasoline usable even months after its expiration date. 

How to Rejuvenate Old Gasoline 

To rejuvenate old gasoline, mix it with new gasoline at a ratio of 1:3. A high-quality, high-octane gasoline is best as this will compensate for some of the old gasoline’s degradation. 

Adding an octane booster will also help as this removes deposits from your fuel lines and your vehicle’s combustion engine, enabling it to run more smoothly. 

Some octane boosters can clean a vehicle’s combustion chamber and the connected fuel lines, which will help the way your engine runs.

Can Fuel Additives Help?

Despite the claims of some manufacturers, no fuel additive can convert old, gummy gasoline into new, fresh fuel.

Most fuel additives are little more than petroleum distillates, which won’t do much for your gasoline, but they might help your engine cope with old gas more effectively. 

Detergent additives remove deposits from your engine’s vital components before they cool and harden.

The best fuel system cleaners are those that contain polyetheramine, or PEA. These products are more effective than those containing polyisobutylene (PIB) or polyisobutylene amine (PIBA).

What Happens When Gasoline Degrades? 

Most of the gasoline sold in the US is ethanol-blend gasoline, which degrades quickly. The ethanol separates from the gasoline within a few months, drawing moisture into the liquid. 

Pure gasoline lasts longer, but after around five to six months, it also starts to degrade. Evaporation and oxidation cause the volatile compounds to break down, making the fuel less combustible. 

The Dangers of Using Old Gasoline 

As gas ages, its different components start to break down. Initially, this causes the gasoline to darken as it separates. This can clog fuel injectors or carburetors, causing your engine to fail.

You can still recondition the gasoline at this stage, but once it appears cloudy or has sediment floating on top, it’s no longer suitable for use. Not even adding new gasoline and additives will make this functional, so you’re better off disposing of it or finding an alternative use for it.   

Ethanol-blend gasoline separates over time, creating two distinct layers, similar to oil on water. This process is called phasic separation and indicates that the fuel is contaminated with water and is no longer safe to use. 

6 Tips on How to Store Gasoline Long Term 

You can extend the lifespan of your emergency gasoline stockpile by following these simple tips:

  1. Fill your gas containers to 95% to reduce moisture build-up and allow for expansion
  2. Add a fuel additive or stabilizer to your gas immediately after purchasing. This will help stabilize the gasoline and lengthen its shelf life.
  3. Store your fuel in tanks rather than your vehicle. This can increase the gasoline’s shelf life to around eight months instead of the three to six months you’ll get if you store it in your car’s tank.
  4. Keep your fuel tanks in a well-ventilated room, away from heat sources and direct sunlight.
  5. Use metal safety fuel cans to store your gasoline. Plastic cans can leach chemicals into the fuel, causing it to degrade faster.
  6. Read our article on how to store gasoline long-term.

What to Do with Old Gasoline 

If your gasoline has separated or become gummy, it’s past the point where you can rejuvenate it with new gas. At this point, you either need to dispose of it through your local household hazardous waste program or find an alternative use for it. 

You can use old gasoline to kill bugs like fire ants, remove weeds, and start fires, but none are environmentally friendly. 


If your gasoline is only a few months past its best-by date, you can rejuvenate it by adding in new, high-quality gasoline at a ratio of one part old gasoline to three parts new. If it has separated or become gummy, it’s too late to restore it to its former glory, and you should take it to a hazardous waste disposal center. 


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