• To make old gas usable, mix it with new gas in a 1:3 ratio. Then, pour in a fuel stabilizer.
• Gas goes bad and is no longer usable when it appears dark, murky, and separates into layers.
• Gas lasts about 3 to 6 months when stored in an air-tight container in a cool, dry place.
• Adding a fuel stabilizer to old gas does not make it like-new again. When it’s added to new gas though, it can extend its life to 1-3 years.

2. Determine whether your gas is old or contaminated.

While old gas can be used in your car, it’s unsafe to use bad gas. To check your gas, pour a bit into a clear glass and compare it to some fresh gas. Fresh gas is a transparent and pale gold, while old gas is a slightly darker amber color. Bad gas usually looks even darker, appears muddy or murky, and is separated into distinct layers.

• Contaminated gas contains debris or sediments; old gas doesn’t.
• Give your old gas a sniff, as well. Bad gas usually smells spoiled or sour.

3. Mix your old gas with new gas in a 1:3 ratio.

The best way to make old gas usable is to dilute it with new gas. Simply fill your car’s fuel tank or a storage tank with 3 gallons (11 l) of fresh gas for every 1 gallon (3 l) of old gas you pour in. Then, gently rock your car or shake the storage tank to mix the gas together.

• Mixing new gas with old gas adds back in the combustive chemicals that evaporated out of the old gas.
• Even when you dilute old gas with new, it won’t be as powerful as fresh gas on its own. Your car might take a few tries to get started.
• If your car is full of old gas, drain its fuel tank with a siphon pump. Store the old gas in a tank to use later, or get rid your gas by taking it to your local recycling or waste disposal centre.

4. Add a fuel stabilizer to extend the life of your gas.

Once your old and new gas is mixed together, just pour in the amount of stabilizer recommended on the bottle to treat the amount of gas in the tank. Fuel stabilizers and additives help prevent the oxidation and evaporation that causes gas to lose its combustibility.