Is your fuel stabilizer actually hurting your car?

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Kyle Smith

Putting your beloved ride away for the season and enduring months of watching it sit in place, wishing you could just go for a drive, is an unfortunate reality of winter vehicle storage. Worse is the notion that your careful storage prep routine includes a common misstep that will set you up for a bad experience come springtime. That’s exactly what FortNine digs into with this latest video about fuel stabilizers:

I am usually the first to throw shade at YouTube “tests” conducted using far from bulletproof science, but even these informal tests shed thought-provoking light on how different chemical compounds affect your car’s performance.

These fuel stabilizers typically have bold claims printed on the label, designed to appeal to the type of person who cares more about protecting their engine than buying the right pet food. I know I am more particular about the fuel I feed my internal combustion companions than the food I feed my fluffy cat friends, but as this video explains, one group has a lot less side effects from corn content.

The ethanol in modern fuel is hygroscopic, meaning it attracts water. That H2O content can reach a point where it will separate from the fuel, especially in long term storage. That water sitting at the bottom of the tank is the first thing to be picked up by the fuel pickup. To address this, the stabilizer concoctions work to lower fuel’s ability to pick up that moisture. They might also add some type of alcohol so that the heavier mixture will burn—however poorly—when drawn into the fuel system and dispersed in the combustion chamber.

Yes, almost all of these mixtures help in some fashion, but a few caused damage in other ways compared to the test’s control sample. A few of the products tested led to greater corrosion, due to a lack of additive preventing the growth of rust and allowing a greater ingress of moisture. That moisture will—at best—make for a hard starting car in the spring and a rusty mess of a fuel system if left alone too long. Our vintage cars often have steel fuel lines and tanks, so any moisture just sitting around is bound to cause trouble.

In the end, the best solution with a vintage engine is to start with non-ethanol fuel. Fuel blends contain a lot of additives already and, as pointed out in the video, if there was one miracle cure that could be added to fuel to prevent all such problems, it would likely already be in the gas from the pump. Ethanol is what causes most of the problems associated with long-term fuel storage in an old car or bike. Barring the option of getting pure gas (also known as recreation gas), K100 and STA-BIL came out on top as recommended from the products sampled because STA-BIL and K100 both reduced the absorption of moisture and reduced corrosion.

Sta-bil gas treatment in drawer
Kyle Smith

Personally, this puts my mind at ease because as I have been a STA-BIL fan for years. Of course, I’ve never had more than my own anecdotal evidence to back up a recommendation, and I am often adding it to ethanol-free fuels from the outset. Now go forth and store with confidence! Hopefully spring arrives sooner than later.

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    Just don’t use more Stabil than recommended it turns to what looks like frog eggs in carburetor fuel bowls that plugs up jets. They will dissolve when air gets to them after opening up the carb. When using fuel with ethanol I store with with a 50/50 mix of Stabil and Marvel Mystery Oil When using ethanol free I use Marvel only. You can’t put to much an it coats fuel system if there is any evaporation. Ever see a corroded two stroke?

    Thanks for this write up.

    BMW Motorrad uses K100 in the tank from the factory, and that is good enough for me.

    Also, with other products such as Stabil, when I have spilled some on my hands they leave a very oily petroleum type film which I have to wash off with a lot of hand soap.

    K100 rinses off with water, telling me it mixes with water-isn’t that the goal?

    I have several machines that go long stretches w/o using, 63 Chevy Impala 283ci, 2003 Buick Park Ave V6, Generac twin 17500w gen, and a twin cyl Cub Cadet lawn tractor. The only fuel these machines ever get is non-ethanol with reg Sta-Bil (3 oz per 5 gal) and over the yrs I’ve never had any fuel related issues. My bro has a large nice Harley but it sat idle the whole of last winter, after I had told him the dangers of using ethanol gas. So warm weather arrived and his bike wouldnt start. The dealer told him not to use E10 gas after he wrote them a ck for $800 bucks. Now he uses non-ethanol and now say he’s gonna stabil nxt winter,we shall see if he’s learned anything.

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