Many or all of the products featured here are from our partners who compensate us. This influences which products we write about and where and how the product appears on a page. However, this does not influence our evaluations. Our opinions are our own. Here is a list of our partners and here's how we make money.
Do fuel additives work? It can be difficult to know for sure without taking apart your engine or tracking data over time.
Most automotive experts agree that properly maintained newer cars won't benefit much from aftermarket fuel additives (the kind you add to your gas tank). These vehicles may show small benefits in longevity and efficiency from pump gasoline with additives such as detergents.
But older or high-mileage cars just might benefit; just beware you're not masking a bigger problem.
If you're wondering if fuel additives really work, here's what you need to know.
What are fuel additives?
Fuel additives are chemicals that can be added to gasoline to improve vehicle performance or help maintain systems. They can serve a variety of purposes, including:
Cleaning systems to remove deposits.
Improving gasoline flow through systems.
Lubricating systems for better operation.
Stopping gas from freezing in tanks.
Preserving gas over long periods of time.
The most common type that drivers see advertised are cleansers that remove carbon deposits from fuel injectors, which pump fuel to the engine cylinders. The fuel comes out as a spray, and when the injectors become clogged with deposits, the amount of fuel that's released can be affected. Cleaner fuel injectors can improve fuel efficiency over time.
Pre-blended versus aftermarket fuel additives
Pre-blended fuel additives
Fuel additives are becoming more common at gas stations as part of pre-mixed fuel options, and many car owners are already using blended gasoline with additives without realizing it. Ethanol, a renewable fuel that helps reduce greenhouse emissions, became a mandated additive for certain fuel in 2005 and has since been a regular sight at pumps with designations of E10, E15 and E85.
Some gas stations offer fuel pre-mixed with detergent additives. For example, Chevron uses its proprietary additive Techron, which it says maximizes gas mileage and minimizes gas emissions.
And Top Tier fuel — a standard by auto manufacturers for blending fuel and additives that's higher than the Environmental Protection Agency's recommendations — is supposed to keep your engine cleaner and avoid buildup on certain components over time. It can be found at most gas stations; look for the Top Tier logo on the pump.
While these pre-blended fuels tend to cost a little more than unaltered fuel, the price difference can be minimal for some brands.
Aftermarket fuel additives
Sometimes called over-the-counter additives, these options are available at retail stores to add to your car independently instead of being pre-blended with fuel at the pump. Additives are available for gasoline- and diesel-fueled cars, and some are marketed for high-mileage or performance cars.
You add the aftermarket fuel additives to your gas tank, where they mix with your gas before it makes its way through the fuel lines. How much you should add and which type depend on your car and its requirements.
All fuel additives have to be registered with the Environmental Protection Agency, but that doesn’t mean the EPA tests additives’ claims. Any additives that claim they're endorsed, certified or approved by the EPA are falsely advertising their qualifications.
But do fuel additives work?
If you're wondering if these additives work, it depends on who you ask and which additive you’re talking about. Manufacturers tend to keep their cards close to their vests, and independent testing of fuel additives is scarce because cars must be driven in consistent conditions to rule out other factors affecting the engine’s performance.
But there are a few independent studies that have gauged whether fuel additives do what they say. According to AAA, a 2016 test showed that cars that used Top Tier fuel had fewer carbon deposits on certain engine components. This finding means that this specific fuel did support engine health and could help car owners with preventative maintenance. The same study also found that using gasoline without Top Tier additives over the long term could reduce fuel economy by up to 4% and increase emissions.
However, not all options have been found to produce the results they promise. Brands like Additech are available as add-ons at the gas pump, and you can have them blended with gasoline on the spot. But one independent study by the National Center for Vehicle Emissions Control and Safety at Colorado State University found that short-term mileage wasn’t improved when Additech was added to fuel.
Taking a chance on additives
It’s impossible to say with certainty that all fuel additives work, but some have shown some benefits for drivers. Not every vehicle will see improvements in performance though, and certain engines as well as older vehicles might have adverse effects if fuel additives run through their systems.
If you’re up for trying a fuel additive and are comfortable with the knowledge that the noticeable difference in performance could be minimal, be smart about the process. Have your vehicle properly inspected beforehand to ensure there are no existing issues that could be worsened by an additive. Then talk with someone who is familiar with your car, such as a certified dealership, to learn about recommended additives for your particular model.
» MORE: How to make your car last longer
Considerations before using fuel additives
If you’re thinking of trying fuel additives, here are a few items to keep in mind.
Manufacturer recommendations. Engines differ from one make and model to the next, and your vehicle’s manufacturer might have recommendations about the use of fuel additives for your model. For example, Subaru states that additives with cleaning detergents will help the boxer engine of some models, and that the use of high-quality fuel with proper additives prohibits the need for over-the-counter additives. Check your owner’s manual for manufacturer recommendations.
Your engine’s current condition. If your engine is already having trouble, you should consider having a mechanic take a look before introducing a fuel additive. It’s unlikely that a fuel additive will correct any major issues, and mixing an additive into the equation has the potential to make an existing problem worse.
Your car’s age. Some experts say that using fuel additives in newer cars is unlikely to bear any fruit. Not only will the cost of the additive outweigh the potential savings in fuel — a bottle of fuel additive with detergents can cost from $5 to $50 — but regular maintenance can keep an engine in good shape without an additive. Older vehicles that weren't well maintained or have a lot of buildup in their engines are better candidates for the advertised benefits of fuel additives.
Your driving habits. According to fuel additive manufacturers, factors like how often you drive your car, the average speed and length of your commute, and temperatures in which your car is driven can affect how fuel additives are supposed to work on your engine. If you use an additive that's not designed for your driving habits and environment, it's unlikely to benefit your vehicle’s performance.
Time to work. Fuel additives don't have an immediate effect on your car’s performance. You’ll need to drive a while, in some cases a few thousand miles, for a cleansing additive to have the marketed effect on your vehicle’s mileage.