Collector cars spend more time as garage queens than they do as road warriors. And that means they sit around—especially through the winter months—with gasoline in the tank. In the old days, this wasn’t as much of a problem, but now our gasoline contains at least 10% ethanol. Ethanol is hygroscopic, meaning it absorbs water from moist air. Gasoline by itself is the opposite, or hydrophobic.
The problem is that if your gas tank absorbs more than 500 parts per million of water in the fuel, it bonds with the ethanol and sinks to the bottom in a process called phase separation. That ethanol/water mix gets sucked into your engine when you try to start it. Not only is the vehicle unlikely to start, but water in the engine promotes corrosion.
One cheap solution is fuel stabilizers that can be added to your tank at the end of the driving season. They work to slow down the unwanted gasoline oxidation process. They’re typically a petroleum product, a mix of antioxidants and lubricants designed to bond with gasoline, repel water and limit both evaporation and winter ice formation. Some add alcohol, so it will mix with the water and at least produce a product that will burn.
Do they work? Tests are somewhat mixed, but when they do work they accomplish an important job. An alternative is to find—easier in some areas than others—ethanol-free fuel and fill up with that before the big layover.
Ford has no official stance on fuel stabilizers, said spokesman Sam Schembari. Porsche actually sells one for its classic cars and says Porsche Classic Fuel Additive dissolves deposits and “forms a protective layer between metal and fuel.” And GM endorses its own division’s ACDelco Fuel System Treatment Plus.
Here are five of the leading stabilizers for collector cars as well as mainstream cars being stored for the winter or summer.
- Sta-Bil Storage Fuel Stabilizer : Best at Protection
- Heet Fuel Additives : Best for Affordability
- Star Tron Enzyme Fuel Treatment : Best Technical Solution
- Royal Purple Max-Clean Fuel Stabilizer : Best for Maybe Saving Money on Gas
- Prevents fuel gelling
- Protects against fuel-filter icing
- Boosts cetin for faster cold starts
- Fit Type: Vehicle Specific
- Package Dimensions: 7.23 L x 4.93 H x 5.75 W (inches)
- Package Weight : 8 pounds
- Cleans, restores, protects the entire fuel system (fuel injectors, carburetors, intake valves and combustion chambers)
- Restores: Lost power, acceleration, lost fuel economy, and operation of the fuel gauge sensor
- Reduces: Rough idle, engine surge, hesitation, and spark plus fouling
- STORAGE – STA-BIL Storage Fuel Stabilizer eliminates the need to drain fuel and keeps gasoline fresh for up to 24 months. Never fear your car or small engine refusing to start due to fouled fuel. This product is effective in all gasoline and ethanol blended fuels including E-10 through E-85.
- ENSURES QUICK, EASY STARTS – Treating your gas with this fuel stabilizer prevents gum, varnish, rust, and corrosion in your fuel tank, all of which are costly to repair. The 32 oz. bottle of this alcohol-free fuel additive treats up to 80 gallons of fuel, and it is perfect to use prior to storing either your vehicle or outdoor power equipment for an extended period.
- VERSATILE – STA-BIL Storage Fuel Stabilizer is safe for use in all gasoline engines, including 2-cycle. Use this fuel treatment in your vehicle, motorcycle, lawn mower, snow blower, boat, and generator.
- No.1 selling brand of premium gas-line antifreeze
- Absorbs 5 times more water than regular gas dryers
- Removes water from fuel system
- Cures and prevents ethanol fuel problems; helps prevent phase separation
- For everyday use and seasonal storage; stabilizes fuel for up to 2 years and can help rejuvenate old, sub-spec fuel
- Makes engines start easily and run smoothly; improves fuel economy and reduces emissions
- Add to fuel to help clean fuel injectors and restore injector spray patterns
- Adds lubricity to upper cylinders
- Helps recover lost MPG and reduce exhaust emissions
- PREVENTS ETHANOL DAMAGE – STA-BIL 360 Protection Ethanol Treatment & Fuel Stabilizer prevents corrosion caused by ethanol blended fuel. Effective in all gasoline blends, including ethanol and non-ethanol, this product helps increase engine power and fuel efficiency.
- STORAGE – Although this fuel additive is engineered for use in fresh fuel at every fill up, it stabilizes fuel for up to 12 months. As America's #1 Ethanol Treatment, you can trust STA-BIL 360 Protection to keep your vehicle or gasoline-powered small engine equipment running at peak performance.
- VERSATILE – The 32 oz. bottle of this alcohol-free fuel additive treats up to 160 gallons of fuel, and it is safe for use in all gasoline engines, including 2-cycle. By preventing the buildup of unwanted gum and varnish, this product is recommended for use in your vehicle, motorcycle, lawn mower, snow blower, boat, generator, and more.
Methodology
Forbes Wheels based its evaluation of fuel stabilizers on the ratings of critics and the manufacturers’ fact sheets, as well as the many online reviews from hands-on users of the products. Finding the stabilizer that’s right for you will depend on how and where you store your car.
An alternative to using these products is to fill up (all the way) with ethanol-free gasoline before putting the car away. It always helps if you start and run your car regularly during the winter, at least once a month. Note: the amount of ethanol that’s actually in E10-style formulations varies by region. There are also E15, E20 and E25 gas-ethanol mixes, representing the percentage of ethanol in the mix.