Consumer Information

Devices and Additives to Improve 

Fuel Economy and Reduce Pollution - 

Do They Really Work?

This document provides information for consumers interested in 

purchasing products that are marketed to improve automotive 

fuel economy and/or reduce automotive pollution. This document 

also includes simple tips for improving fuel economy and reducing 

automotive emissions.

Watch Out!

Consumers are looking for simple and inexpensive means to lower the cost of driving. The market has responded with a plethora of devices and fuel additive products 

which purport to improve fuel economy and/or reduce emissions. Have you seen 

advertisements that claim to “Double Your Fuel Economy,” or that promote a device 

that “Cleans-up Your Car’s Tailpipe Exhaust”? Be careful when purchasing these 

products; don’t be fooled by erroneous claims. Thoroughly research any aftermarket 

part or additive before you add it to your vehicle and don’t forget the old adage, “If it 

sounds too good to be true, it probably is.”

Please visit the following Federal Trade Commission links: FTC Consumer Alert at 

www.ftc.gov/bcp/edu/pubs/consumer/alerts/alt095.shtm and Fact Sheet for Consumers on Gas Saving Products at www.ftc.gov/bcp/edu/pubs/consumer/autos/aut10.pdf.

Fuel Additives 

Many fuel additives are advertised to improve fuel economy, reduce exhaust emissions, or both. Some advertisements claim these products have been endorsed or 

approved by EPA. However, EPA does not endorse, approve, or certify fuel additives.

EPA does require fuel additives to be ‘registered’ but EPA does not test candidate 

products for engine efficiency, emissions benefits, or safety as part of the registration 

process. To register an additive, manufactures must report the chemical composition 

Office of Transportation and Air Quality

EPA-420-F-11-036

 August 2011
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along with certain technical, marketing, and health effects information. In some cases the manufacturer may be required to conduct testing or literature research to assess potential emissions 

health effects. The EPA registration process does not include a check of manufacturer product 

efficacy claims. In other words, EPA does not determine whether or not the fuel additive works 

as advertised. Registration does not represent EPA endorsement of the product.

The following are links to all registered fuel additives for: 

Gasoline: www.epa.gov/otaq/regs/fuels/additive/web-gas.htm

Diesel: www.epa.gov/otaq/regs/fuels/additive/web-dies.htm

Detergents: www.epa.gov/otaq/regs/fuels/additive/detergnt/web-dtrg.htm

Do NOT assume that because a fuel additive has been registered with EPA that this implies 

anything about the safety, benefits, or claims made by the manufacturer. 

Aftermarket Devices to Improve Fuel Economy or Reduce Emissions

Any additions or changes to your car’s engine, emission system, fuel system, or exhaust system 

have the potential to cause one or more of the following problems: 

•	 Increased emissions

•	 Reduced fuel economy

•	 Harm to your car

•	 Void the manufacturer warranty

•	 Create safety or environmental hazards

•	 Violate the federal prohibition against tampering (EPA, Office of Enforcement www.epa.

gov/compliance/resources/policies/civil/caa/mobile/vehicleengine-penalty-policy.pdf)

If a marketed device has significant benefits, the manufacturer may submit data to the EPA and 

apply for EPA testing through the Voluntary Aftermarket Retrofit Device Evaluation Program.

Very few manufacturers have applied for this program in the past 10 years. Most devices tested

in earlier years had a neutral or negative effect on fuel economy and/or exhaust emissions. If the 

manufacturer has submitted the aftermarket device for testing, you can find the report on the 

EPA’s findings here: www.epa.gov/otaq/consumer/reports.htm. Unless EPA has an Aftermarket 

Retrofit Device Program report, EPA has no information about the impact of the device or additive on fuel efficiency, the environment, or the safety of adding this device to your vehicle.

Popular Devices and Their Effects on Fuel Economy and Automotive Emissions

• Devices That Turn Water Into Fuel 

There are many advertisements about using the energy from your car’s battery to split 

water molecules into hydrogen and oxygen gas which is then burned with your fuel. EPA 

has received no credible and complete data showing a positive fuel economy benefit from 

these devices. 

Installation instructions for some of these devices call for adjustments that EPA would 

consider to be tampering. The Clean Air Act prohibits tampering with your car’s emissions control system. Tampering violations are punishable by significant fines (EPA,
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Office of Enforcement www.epa.gov/compliance/resources/policies/civil/caa/mobile/

vehicleengine-penalty-policy.pdf). Any instructions that request you adjust the air/fuel 

ratio on your vehicle, or adjust a knob and listen for the engine to misfire, referred to as 

feeling vibrations or stuttering, are in violation of the prohibition against tampering.

• Fuel Line Devices

	 You may see advertisements for devices that heat, magnetize, ionize, irradiate, or add

metals to your vehicle’s fuel lines and purport to increase your vehicle’s fuel economy 

and reduce exhaust emissions. EPA testing and engineering analysis of such devices to 

date has shown no substantive effect on fuel economy or exhaust emissions. Installation 

of devices that retard timing or adjust the air-fuel ratio of the vehicle may be considered 

tampering.

• Mixture Enhancers

Several heavily marketed devices claim to increase your vehicle’s fuel efficiency by creating aerodynamic properties or turbulence that improves the air-fuel mix prior to combustion. EPA has received no credible and complete data showing positive fuel economy 

benefits from these devices.

Aftermarket Alternative Fuel Conversions

Like fuel additives and aftermarket devices, aftermarket alternative fuel conversions are sometimes touted as a way for consumers to save money, improve fuel economy, and reduce pollution. 

But once again, consumers need to be wary of such claims. Conversions may make sense in some 

cases, but it is very difficult to re-engineer a vehicle to operate properly on a different fuel than 

the one for which it was originally designed. It is especially difficult to ensure that the vehicle 

will meet emission standards on the new fuel over the vehicle’s full useful life. Therefore it is 

important to educate yourself thoroughly before altering your car to run on an alternative fuel. 

Here are some factors to be aware of if you are considering a conversion:

•	 Some fuels have a reputation of being inherently “clean” but in today’s vehicles it is not

the fuel alone but rather the sophisticated integration of engine, fueling, exhaust and 

evaporative emission control system designs that determine how clean a vehicle will be. 

Vehicle conversion systems must retain a similarly integrated design logic and functionality in order for emissions to remain low.

•	 Gaseous and alcohol fuels are less energy dense than conventional fuels, so you cannot travel as many miles between re-fueling, and your fuel efficiency per gallon of fuel 

will decrease compared to gasoline or diesel. It is also difficult to re-optimize an engine

for fuel efficiency on a new fuel, so an alternative fuel conversion may be less efficient 

than an engine that was designed to run an alternative fuel in its original design. Understanding these issues is critical to accurately compare the costs of running your car on 

its original fuel and the costs of running your car on a new fuel with an aftermarket fuel 

conversion.

•	 Be sure to check whether your vehicle’s manufacturer will continue to honor the warranty after conversion.
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In order to ensure that your vehicle will meet the same emission standards that the original 

vehicle was required to meet, EPA has established regulations that must be followed to avoid 

violating the federal prohibition against tampering (EPA, Office of Enforcement www.epa.gov/

compliance/resources/policies/civil/caa/mobile/vehicleengine-penalty-policy.pdf). If the conversion manufacturer has not followed EPA regulations and guidelines, you may be violating the 

tampering prohibition, which carries a significant fine, and you may be increasing the release of 

harmful exhaust and evaporative emissions into the environment.

So, What Can I Do to Improve my Fuel Economy and/or Reduce 

Automotive Emissions?

There are several things you can do obtain the best possible fuel economy and produce the lowest possible emissions.

•	 Avoid idling. Idling the engine wastes fuel and produces unnecessary pollution. Shut

off the engine while waiting in traffic delays or while conducting drive-up transactions. 

Modern cars do not benefit from idling to warm up in cold weather. 

•	 Check tire pressure regularly. Keep your tires inflated to their recommended pressure.

•	 Take action if your check engine light comes on. If the check engine light is illuminated,

take your vehicle to a mechanic that has check engine (OBD) code reading capabilities

and repair any malfunctioning parts.

•	 Drive sensibly and observe speed limits. Driving fast and/or aggressively (rapid acceleration and hard braking) can significantly reduce your fuel economy. Cruise control is a 

good way to regulate your highway speeds.

•	 Perform regular vehicle maintenance. Follow the manufacturer’s recommended maintenance schedule.

•	 Plan your trips. Get all of your errands done at once. Your engine is more efficient when

it is warmed up, so one long trip is better for your car’s efficiency than many short trips. 

Don’t forget to carpool when possible.

•	 Minimize vehicle weight and maximize aerodynamics. Think before you put something

big on top of your car or something heavy in, on, or towed-behind your car. For example, 

a car roof-top carrier will increase the vehicle’s frontal surface area and drag coefficients 

which will reduce your fuel economy. Adding mass to your car will also decrease fuel 

economy, so if you don’t need it, don’t carry it in or on your car. 

•	 If you are shopping for a new or used car, use EPA’s Green Vehicle Guide www.epa.gov/ 

greenvehicles to compare 2000 through present model year vehicles for fuel economy. 

The following websites offer additional advice about how to improve your fuel economy and 

reduce your automotive emissions.

www.fueleconomy.gov/feg/drive.shtml

www.epa.gov/otaq/consumer/17-tips.htm

www.epa.gov/fueleconomy/whatyoucando.htm

www.epa.gov/otaq/consumer/18-youdo.htm

www.eere.energy.gov/afdc/vehicles/fuel_economy_light.html

www.eere.energy.gov/afdc/vehicles/fuel_economy_heavy.html
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For More Information

Federal Trade Commission Consumer Alert 

www.ftc.gov/bcp/edu/pubs/consumer/alerts/alt095.shtm

Federal Trade Commission Fact Sheet: “Gas Saving” Products

www.ftc.gov/bcp/edu/pubs/consumer/autos/aut10.pdf

EPA Office of Transportation Air Quality Compliance Information Hotline 

Phone Number: 734-214-4343

Email: Complianceinfo@epa.gov