Every piece of advice about laying something up eventually covers the same ground, and fuel usually gets one line: add stabilizer. That one line usually does more work than almost anything you need to do to store your property for extended periods, and it hardly scratches the surface of why you are doing what you are doing.
Why fuel is the real risk
Gasoline starts breaking down the moment it is made, and modern gasoline breaks down faster than the stuff from a few decades ago. Most gas today is blended with ethanol, commonly ten percent (E10). Here is the short version of why that matters: oil and water do not mix, and gasoline behaves like oil.
Ethanol is different. It can mix with gasoline and water at the same time, almost as if it has one hand that holds onto gasoline and another that holds onto water, bringing them together. That is how it quietly pulls moisture from the air and keeps it dissolved in the fuel without you ever noticing.
But ethanol can only hold so much water. Past that point, it lets go of the gasoline and grabs onto the water instead, and the two clump together, get heavier than the gasoline, and sink to the bottom of the tank. That is phase separation. Once that happens, to put it plainly, “you’re up the creek ... you’re screwed.” You have two different liquids in one tank, and no amount of stabilizer added afterward will fix it.
How long does fuel actually last
These are general ranges, not guarantees, and heat, humidity, and how full the tank is all shift the numbers:
- Ethanol-blended gasoline, untreated, can start degrading within 30 days and is commonly considered unreliable after 2 to 3 months.
- Ethanol-free gasoline, untreated, usually lasts longer, often 6 months to a year, since there is no ethanol to pull in moisture.
- Treated gasoline, either type, with stabilizer added at fill-up can reasonably extend to 12 to 24 months, depending on the product. Stabilizer slows the breakdown. It does not stop it.
- Diesel is more stable than gasoline because ethanol is not a factor. It is typically good for 6 to 12 months untreated, and longer in cooler storage. The real enemy of stored diesel is water and the microbial growth it invites, often called “diesel bug,” which biocide additives are meant to address. Ask me about my grandpa’s ’86 Kubota and how much fun it is to remove bacteria from a diesel tank.
- Two-stroke pre-mix, with gas and oil already combined, degrades faster than straight gasoline because the oil and fuel can separate over time. Most guidance recommends using pre-mixed fuel within 30 to 60 days, less if it is made with ethanol-blended gas and more if it is ethanol-free and stabilized.
- Propane essentially does not go bad. The tank and its valves age. The propane itself does not.
I have seen gasoline go bad faster than the range above suggests, and my best guess is a bad batch from that particular station rather than anything I did wrong. That is worth keeping in mind for a reason beyond just my bad luck: not every gallon of “regular unleaded” is the same. Many stations pull from the same regional terminal and differ only in the additive package their brand adds on top, while others source from an entirely different terminal. A contaminated delivery, an underground tank that needed cleaning, or just a thinner additive package can knock real time off that specific fuel’s estimate. Treat the ranges above as a general guide, not a guarantee for the specific fuel sitting in your tank.
The debate that will not die
Fill the tank all the way, or run it dry. Both camps have a real point. A full tank leaves less room for moist air to condense inside it, while any air space left behind, even in a tank that is just short of full, gives that moisture somewhere to collect. A freeze-thaw cycle makes it worse: the air in that space expands and contracts with each temperature swing, leaving a bit more condensation behind each time.
Running dry prevents fuel from going bad in the first place, but it rarely gets every drop out of the lines or the carburetor, and whatever is left behind is exactly what varnishes and gums things up over the winter, unless it was treated fuel to begin with. If you are going to run it dry, run treated fuel through it first, so whatever is left behind in the lines and carburetor is already stabilized. If you fill it, treat what you put in with care. The stabilizer is the part actually doing the work, not whichever side of the debate you picked.
Which side makes more sense for you depends on your situation, how much freeze-thaw and humidity your area actually experiences, and how soon you plan to use it again. One case tips the scale clearly: if you already know you are looking at more than a year of sitting, drain it and clean the system instead of relying on a full tank. A stabilizer can reasonably carry treated fuel for about a year. Past that, you are betting on the fuel outlasting the stabilizer, and that is a bet you will probably lose.
More stabilizer is not automatically better. A small overdose shouldn't hurt anything, but dumping in well beyond what the bottle calls for, especially more than once, can leave its own residue behind, gum up injectors or carburetor passages, and soften old rubber seals and gaskets over time. That is exactly why most stabilizers come with a measuring cap or spout calibrated to a specific ratio, often a single small cap for several gallons. Read the ratio once and use it, rather than guessing at a heavier pour just to be safe.
Knowing the actual capacity of what you are treating is most of the battle. For small engines, mixing the correct ratio in a separate 1- to 5-gallon container first, then running that pre-mixed fuel through the equipment, is more reliable than eyeballing a dose straight into a small tank. For a car, boat, or anything with a larger tank, know the tank’s capacity, pour the stabilizer in first, then fill the rest of the way with fuel, and run the engine for a minute or so afterward. That last step matters: it circulates the treated fuel through the lines and carburetor instead of leaving it sitting untouched in the tank, which trades a tank of treated fuel for a carburetor that gums up anyway.
Regular unleaded is 87, midgrade is usually 89, and premium is either 91 or 93, depending on where you live. That covers what most people are actually pumping, and regular, midgrade, and premium are typically all the same: ten percent ethanol (E10). The octane difference comes from the gasoline blended underneath, not the ethanol. Fun fact: Colorado and a few other high-altitude states sell 85 as regular instead of 87, since thinner air at elevation means an engine needs less octane to avoid knocking. Octane has nothing to do with how long fuel lasts in storage; that depends on ethanol content, as noted above. Ethanol-free, where it is sold, is a separate label from octane rather than a fourth grade on that same scale, but it is often sold as “race” fuel.
For anything you do not use often, such as a generator, a snowblower, or a boat that sits more than it runs, skip the debate entirely. Just assume it is going into storage. Run treated fuel through it before it sits, so the tank, lines, and carburetor all have stabilized fuel in them instead of whatever was already there. Mark down when you filled it, what octane, and which stabilizer you used, somewhere you will actually find it again, which is exactly the kind of thing goFrigg is built to hold onto. Next time something will not start, that record tells you in ten seconds whether the fuel is even a suspect.
Fuel cells: batteries do not all fail the same way
Small household batteries, AA, AAA, and similar sizes, have a genuinely long shelf life, often 5 to 10 years when unused. The real risk during a long layup is leaving them inside a device. Alkaline batteries can still leak after months of sitting, and that leak can ruin whatever they were sitting in. Pull them out before something goes into storage. It is as simple as that.
A 12-volt lead-acid battery, the starting or deep-cycle battery in a car, boat, or similar vehicle, is a different animal. It self-discharges over time, even when doing nothing, and a battery left sitting at a low charge for weeks can develop sulfation, a buildup on the plates that permanently reduces its capacity to hold charge. A smart battery maintainer during storage solves this, since it regulates the charge and shuts off once the battery is full, rather than feeding it a constant current as an old-style trickle charger does, which can overcharge a battery left connected for months. Disconnecting the terminals slows self-discharge if you do not have one, a method I see routinely at the boatyard. Just check the status with a multimeter or a load tester before tucking it away, to be sure.
Tool batteries, the lithium-ion packs behind cordless platforms like Milwaukee, EGO, Makita, and DeWalt, behave differently again. Lithium-ion batteries do not like sitting for months fully charged or fully discharged. Most manufacturers recommend storing packs at around 40 to 60 percent charge, in a place with moderate temperature, and checking on them occasionally rather than leaving them untouched on a shelf all winter.
None of that is complicated once you know it. It is just three different chemistries, each with its own way of quietly failing if you assume “battery” means one thing.
Fuel and batteries are two things almost everything you own has in common, no matter what it is or how you use it, and they are also two of the most common reasons something will not start again in spring. Everything else on a layup checklist matters too. This is the part that is easy to skip and expensive to have skipped.