The Best Fuel Stabilizers For 2022

Sta-Bil makes big claims—it guarantees it will keep fuel fresh for up to two years–and backs that up with some impressive test results. The formula uses a highly purified petroleum distillate but the formula is a trade secret. The company says it does not contain alcohol. You use one ounce for every 2.5 gallons of gas in the tank. Sta-Bil works for all gas engines, including two-cycle types, and says it prevents gum and varnish build-up. Briggs & Stratton, the small engine company, recommends it, and there are variants formulated for diesels and marine engines. Sta-Bil comes out on top  in this test, which measured both how much water/ethanol mix was taken on, and how flammable that mix became. It also does pretty well against winter ice formation.

Gold Eagle produces both Heet, which is methanol-based, and Iso-Heet, which is largely isopropyl alcohol. The company claims its Iso-Heet stabilizer absorbs five times more water than regular gas dryers, and also prevents rust and corrosion. (You could just use drugstore isopropyl alcohol, but Heet is actually cheaper.) It performed well in tests conducted at the University of Nebraska Lincoln. The researchers found it “increased the water-holding by 0.23 teaspoons per gallon, a seven percent increase over E10 [without additives].” Heet (yellow bottle) did well a comprehensive test by Project Farm against Sea Form stabilizer.

This product is concentrated, so eight ounces is said to treat 48 gallons, meaning one bottle is good for the fuel left in the tank of most stored vehicles. It’s a combination of proprietary enzymes in a fuel suspension. It’s formulated for E10 engines. The company claims that, like Sta-Bil, it can protect unused fuel for two years. It works to fight phase separation dispersing the built-up water through the fuel as submicron-sized droplets. Dirt Wheels magazine tested Star Tron in its fleet of new and used ATVs, plus a generator, during a six-month layover and was “very impressed with the results. So far, since these engines have been up and running, we have not had any issues….In fact, the generator actually seems to start quicker and doesn’t suffer from a rough idle anymore. If the Star Tron fuel stabilizer keeps working this well, we will consider it cheap insurance.”

Are clean engines more powerful and more frugal? So claims Royal Purple, which says that its product, when used as a regular additive, improves fuel economy an average of 3.2 percent, and increases horsepower by 2.6%—while also reducing hydrocarbons (12%), NOx (13%) and CO (18%). These are unverified claims and we retain some skepticism, but the improvement is affirmed (to some degree) by users. One noticed a 1-2 mpg improvement for every six to seven tank fills. Another went from 25.6 mpg in his 2012 Chevy Sonic to 29.1 two weeks later. “It appears to be doing exactly what it says it does,” the owner said. Honda Shadow, Ram truck, Kia Optima turbo and even Geo Metro owners report power perceived increases.

NAPA Know How, using a can of Max-Clean as illustration, gives credence to the power and horsepower claims. “As the build-up grows,” NAPA said, “the level of fuel that can pass is reduced, meaning the engine loses power, the fuel economy suffers and the drivability of the car is diminished.” Of course, the product can also be used as a stabilizer. This test studying engine carbon build-up found modest but “impressive” results from Max-Clean.