VFMany of us own gasoline powered generators and other power tools that run on gasoline. Despite the fact that this is one of the most commonly used types of fuels, many people don’t know that it has a relatively short shelf life. Some say that untreated gas only has a shelf life of about three months but in my experience, that might be stretching it a bit.
If you store gasoline in an engine like a backup generator so that it will always be ready when you need it, there’s a good chance that your generator won’t start when you need it the most. Gasoline WILL go stale when it is stored for very long. In addition to it becoming less combustible, other things can happen to it. For example, water condensation can accumulate inside the container, and as I’m sure you know, water doesn’t burn too well in any engine.
Another thing that can happen is a process called “oxidation” which can reduce the octane quality of the gasoline. This can also result in sludge like deposits accumulating in the tiny orifices of your engine’s carburetor. If you allow this to happen, simply draining out the old gasoline and replacing it with fresh gas won’t help you a bit. Your engine still won’t run because the new fresh gas won’t be able to flow properly through the carburetor. You’ll need to pull the carburetor and give it a thorough cleaning with carburetor cleaner.
What Can You Do To Prolong The Life Of Gasoline?
No matter what you do, gas cannot be stored indefinitely. You can, however, do some things to prolong its shelf life. Anytime you will be storing gasoline for any length of time, you should add a fuel stabilizing chemical such as STA-BIL® to the gas. The company that makes this product guarantees that it will make stored gas last at least a year. They also imply that doubling the recommended ratio of their product to the gas that you are storing may make the gasoline last up to two years. They do point out that gasoline that is over a year old tends to lose its ignitability. This can result in hard starting or poor running engines.
Adding a fuel stabilizer is the first step but it’s not the only step. Keep in mind that if you add this product to your gas tank, the gas that is in the fuel lines, fuel filter, and carburetor has not been treated and it will go stale. To prevent this, I like to add treated fuel to the tank and then run it long enough to ensure that all of the untreated fuel has been used up.
If I decide to leave gasoline for a few months in my engine’s fuel tanks, I like to keep the tanks completely topped off. The lower the level of gas in the tank is, the more evaporation will take place and the more water condensation may tend to accumulate.
Stale Gas Cannot Be Saved By Adding Stabilizer
Once gas has already gone stale, it’s too late to add fuel stabilizer to it since the degradation of the fuel has already taken place. I’ve had some success when I’ve mixed old gasoline with new gasoline for use in non-critical tools like lawn mowers and rototillers. Having said that, I would never suggest running old fuel in critical tools like generators.
What About Treating Diesel Fuel
Diesel fuel may last a bit longer without treatment but it will degrade as well if left untreated. Be sure and only use fuel stabilizer that is designed for diesel fuel if you are going to use it. The same advice about keeping stored tanks topped off also applies to storing diesel fuel.
If Fuel Doesn’t Store Well, How Can You Stockpile It?
My advice would be that instead of storing gasoline or diesel fuel for long periods of time, you cycle through it. If you happen to live in an area where it is legal to store gasoline in farm storage tanks, you might consider having these tanks filled and then use the fuel in your power tools and vehicles when you need it instead of filling up at your local gas station.
I know a lot of farmers and ranchers who have their large fuel storage tanks regularly topped off when the delivery trucks make their rounds. This gives them the ability to have plenty of fuel on hand but they use it fast enough that it doesn’t have a chance to go stale. If you choose to go this route, be sure and have a fuel filter installed that you can easily drain any water out that may accumulate in the tanks.
The other option, and the one that we use, is to cycle through our stored fuel. We keep enough on hand to power our generators and tractor but we also keep a little in reserve. Once a month, we run the fuel that we have been storing in our cars, power tools, and tractor and we replace it with fresh fuel. This gives us the ability to keep about a months worth of excess fuel on hand without needing to worry about it going bad.
Any of our power tools that won’t be used for a while have a small amount of treated fuel added to them and then they are run until the treated fuel has had a chance to cycle through all of the components of the engine. We then drain the fuel out of the tanks and carburetors and use it in other engines. This way, tools that are put into storage aren’t stored with fuel in them and any remaining fuel that we aren’t able to get drained out has been treated with a stabilizing chemical. When it comes time to pull these engines out of storage, we just add fresh fuel which makes them much easier to get started than if we would have left untreated gasoline in them for a prolonged period of time.
Note: Be sure that you check with your local authorities about how much gasoline you are legally allowed to store where you live and how it must be stored. Also, be sure that you read the owners manual for your particular generator to see how they recommend storing fuel in them. Over everything else, follow their directions.