As a prepper, you probably have some old gas sitting around. Maybe it’s for a rainy day supply in case of disaster, or maybe you keep a quantity on hand to operate your tools. Whatever the case, if you don’t stay on top of rotating it, your gasoline can get old and go bad.
Some folks claim it’s possible to recondition old gasoline by mixing it with new, fresh gas. It’s certainly doable, but should you? Is it a good idea to mix old gas with new gas, or not?
Yes, you can mix old gas with new gas so long as the old gas has not deteriorated to the point of uselessness. Depending on the age of the gasoline, mixing in new can salvage the old supply and make it usable.
This is an old trick that’s been around for quite a while, and one that still works today. However, you’ll need to know what kind of gas you are dealing with as well as how to assess the old gas for viability and how to mix your new gas in with it properly and safely.
I’ll tell you how to do all of the above in the rest of this article…
Is Old Gasoline a Problem?
Yes, old gasoline is a big problem most of the time. Gasoline has a shelf life, it expires.
As gasoline gets older, it starts to break down, meaning the volatile compounds that make gasoline a useful and usable fuel will start to degrade. This means it will not function in engines as efficiently or as reliably.
Worse yet, modern gasoline that has ethanol in it will start to separate over time, basically ruining it. Regrettably, ethanol blends are most of what is sold at the consumer level!
The shelf life of your gasoline depends on whether or not it has ethanol in it, but generally you should only expect between 3 and 6 months from it if stored in ideal conditions. If your gasoline is not too far gone, you can it safely mix it with new stuff to revive it.
Why Would You Mix Old Gas with New Gas?
By mixing new, fresh and viable gasoline with your old stuff that’s starting to break down, it is possible to blend the two together and make the old stuff usable so it doesn’t go to waste. This is a good way to save a little bit of money, and might be the only way to maximize your gasoline supply when you’re in a real jam.
Note that you cannot simply add old and questionable gas to new gas and have it work every time: the old gas is too old and degraded, it’s still likely to cause a malfunction in your engine or even fail entirely and you’ll have wasted the new stuff too!
How Can You Tell When Old Gas is Too Far Gone?
It’s fairly easy to tell when you’re gasoline is starting to go bad. Pouring it into a clear container helps with the assessment. First, look for major disqualifiers, indicators that your gas is just too old to risk using.
If your gasoline supply looks cloudy, milky or opaque, don’t waste your time. If it’s showing any signs of a slime or film growing on the surface (or drifting around throughout), don’t chance it.
Also, if the gasoline has ethanol in it, look for two or more distinct layers in your gasoline, sort of like an oil slick floating on top of water, that is an indicator of phasic separation and the gas is ruined. Discard!
Next, check for indicators of age that might mean it is still viable. If your gasoline has simply noticeably darkened or has a reddish tint to it, it’s probably okay to use if you can mix it with new stuff.
Similarly, any small particulates that might be floating in it might just be a sign of contamination from dirt or other debris, or potentially rust from inside of a metal container. If you can strain the gas and then mix it with new, it should work.
When is it Okay to Mix Old Gas with New Gas?
Assuming you’re willing to risk degraded performance and, potentially, malfunction in any engine that you use the gas in, you can mix your old gas with new gas so long as it passes the quality standards detailed in the previous section.
Mixing Gas the Right Way
Mixing gasoline is very straightforward: all you need is a container to mix the two in, and equal parts of the old stuff and new stuff.
Carefully pour the old gasoline into a fresh container, taking care to strain it if required. Then, add an equal amount of new gasoline to the container. Cap the container and then it rock or slosh it back and forth for about a minute. You’re done!
Now use your mixed fuel to gas up your vehicle or whatever tool you’re trying to use and then try to start. Be warned that it will probably be more difficult to start and may run a little rougher, but it should work if your old gas wasn’t too far gone.
Don’t Forget to Use Additives When Needed!
One thing that can save you a ton of grief when it comes to storing gasoline is fuel stabilizer.
Adding a blend-specific fuel stabilizer to any quantity of fresh gasoline will greatly extend its shelf life before it goes bad. You might get a 50% or even 100% increase in overall shelf life; pretty impressive!
Just make sure you buy the product that is specified for your gasoline: generally speaking, ethanol gasoline blends will require a specific product while pure gasoline blends take a different one.
Once you have it, simply add the quantity required to your cans or drums according to the package directions, stir or shake, and you are good to go.
Tom Marlowe practically grew up with a gun in his hand, and has held all kinds of jobs in the gun industry: range safety, sales, instruction and consulting, Tom has the experience to help civilian shooters figure out what will work best for them.
Good reminders. Tom. However, more specific information would be appreciated. Sta-Bil vs Star-Tron vs AmSoil vs PriG?