Old gasoline is something many people forget about until it becomes a problem. It might be sitting in your garage, stored in a jerrycan, or left over in your lawn mower, generator, or boat. Unlike wine, gasoline does not get better with age. In fact, when it gets too old, it can damage your engines, create safety hazards, and harm the environment.
Knowing how to deal with old gasoline is important for your safety, the health of your equipment, and the cleanliness of the environment. This article explains what old gasoline is, how to tell if it’s gone bad, and the best ways to handle and dispose of it.
What Is Old Gasoline?
Gasoline is a refined petroleum product. It’s a mixture of many hydrocarbons and additives designed to keep engines running smoothly. Over time, this mixture begins to break down. Exposure to air, heat, and moisture causes it to oxidize. When that happens, the gasoline loses its power and can become gummy or thick.
Generally, gasoline starts to degrade after 30 days, especially if it’s not stored properly. Ethanol-blended gasoline, which is common in the U.S., absorbs water from the air. This makes it go bad faster. Depending on the storage conditions, gasoline might stay usable for three to six months, but after that, it’s risky.
How Can You Tell If Gasoline Is Bad?
You don’t need to be a fuel expert to recognize old gasoline. Here are some signs that gas has gone bad:
Smell
Fresh gasoline has a sharp, sweet smell. Old gas smells sour, like varnish or paint thinner. If it doesn’t smell like the fuel you remember from the pump, it’s probably gone bad.
Color
Gasoline should be clear and pale yellow. If it looks darker, cloudy, or has rust particles in it, that’s a sign of aging or contamination.
Texture
When gas becomes old, it can feel thicker and stickier. If you pour it into a clear container and see layers forming, or if it leaves a residue, it’s likely unusable.
Engine Performance
If your engine won’t start, stalls, or sputters after using stored gas, the fuel might be the problem. Old gasoline loses its combustibility, so engines can’t run properly on it.
Why You Shouldn’t Use Old Gasoline
Using old gasoline can cause real problems. It’s not just about poor engine performance — it can also damage the engine itself.
Gum and Varnish Buildup
As gasoline oxidizes, it forms sticky residues. These can clog fuel injectors, carburetors, and filters. Over time, they lead to expensive repairs.
Corrosion
Ethanol in fuel attracts moisture. When water mixes with gasoline, it causes corrosion in metal fuel tanks and engine parts.
Fuel Separation
Old gasoline can separate into layers. If water or ethanol separates out and gets into the engine, it won’t ignite properly. This leads to misfires, knocking, or no ignition at all.
Can Old Gasoline Be Reused?
Sometimes, old gasoline can still be used, but only in limited ways and only if it’s not too degraded. Here are some tips for reusing slightly old gasoline safely:
Mix With Fresh Gas
If the gasoline is only a few months old and doesn’t smell too bad, you might be able to dilute it with fresh fuel. A 1:4 ratio (one part old, four parts fresh) can make the old gas usable in less sensitive engines like lawnmowers or chainsaws.
Use in Equipment With Simple Engines
Small engines without fuel injection systems are more forgiving. A lawnmower or snow blower might tolerate slightly old gas better than a car or boat.
Important: Never mix or reuse gasoline if it smells foul, looks dark or sludgy, or has water in it.
How to Safely Dispose of Old Gasoline
Disposing of old gasoline the wrong way can be dangerous. You should never pour it down a drain, throw it in the trash, or leave it in the soil. It pollutes the environment and can cause fires or toxic fumes.
Here are safe steps for disposing of it properly:
Step 1: Store the Gasoline Safely
Use a proper fuel-approved container. Make sure it’s tightly sealed and labeled clearly as “old gasoline – for disposal.” Keep it away from children, pets, and open flames.
Step 2: Check Local Regulations
Every city or county has different rules about hazardous waste disposal. Contact your local waste management office, fire department, or recycling center. Many areas have dedicated drop-off days or facilities for hazardous waste.
Step 3: Take It to a Disposal Site
Take your old gas to an approved collection center. These may include:
- Household hazardous waste facilities
- Auto repair shops
- Fire departments
- Recycling centers
Some garages or dealerships will accept old gas for recycling or disposal, especially if you’re getting a vehicle serviced.
Step 4: Clean the Container
After safely disposing of the fuel, clean the container thoroughly. Rinse it with fresh gasoline (not water) to remove residues, then let it dry before using it again.
What About Fuel Stabilizers?
If you want to store gasoline for a longer period, you can use a fuel stabilizer. These additives slow the aging process and keep the fuel from breaking down so quickly.
How Fuel Stabilizers Work
Stabilizers bond with gasoline to protect it from oxidation and moisture absorption. They help prevent gum and varnish from forming. When used correctly, they can extend fuel life from a few months to over a year.
When to Use Them
Use stabilizers if:
- You’re storing gasoline for emergency use.
- You’re putting your lawn mower, boat, or RV away for winter.
- You have a backup generator that sits unused most of the year.
Always add the stabilizer to fresh gas, not old gas. Follow the instructions on the product label for correct mixing ratios.
Tips for Storing Gasoline Safely
Proper storage is the best way to avoid having to deal with old gasoline in the first place.
Use the Right Container
Only store gasoline in containers specifically designed for fuel. These are made of materials that resist corrosion and are built to prevent leaks.
Store in a Cool, Dry Place
Heat accelerates the breakdown of gasoline. Keep it in a garage or shed that stays cool and dry. Avoid direct sunlight or areas near heat sources.
Keep It Sealed
Always tightly seal your gas containers. Exposure to air speeds up oxidation and allows moisture in.
Label Your Containers
Clearly mark each container with the date you filled it. This helps you track how old the gasoline is.
What Happens If You Accidentally Use Old Gasoline?
If you’ve already used old gasoline and your engine is running poorly, here’s what you can do:
Drain the Fuel Tank
Remove the old gasoline from the tank. Use a siphon pump to avoid contact with skin or breathing in fumes.
Clean or Replace the Fuel Filter
The filter may have caught gunk or water from the old gas. Clean it if possible, or replace it with a new one.
Add Fresh Fuel and Stabilizer
Once you’ve emptied the tank, refill it with fresh gasoline and add a stabilizer to clean the system.
Run the Engine
Let the engine run for a few minutes to circulate the new gas through the system. It may take a little time to return to normal.
If problems continue, the carburetor or injectors may need cleaning.
Conclusion
Old gasoline can be a hidden hazard in your garage, shed, or vehicle. It’s easy to forget that fuel has a shelf life, but once it degrades, it can damage engines, create safety risks, and harm the environment. Thankfully, with proper storage, fuel stabilizers, and safe disposal methods, you can avoid these problems.
If you come across old gasoline, don’t panic. Use your senses to test it, decide if it can be reused safely, and if not, follow the right steps to get rid of it responsibly. Taking a few extra precautions now can save you time, money, and stress later on.
Whether you’re a homeowner, mechanic, or just someone with a forgotten gas can in the shed, knowing how to deal with old gasoline is a useful skill that keeps you, your equipment, and the planet safer.