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EPA - Aftermarket Retrofit Device Evaluation Program



EPA conducts a voluntary program to evaluate aftermarket devices and fuel additives that manufacturers claim will improve fuel economy and/or reduce exhaust emissions for passenger cars and trucks. The purpose of the Aftermarket Retrofit Device Evaluation Program (also known as the "511 Program") is to generate, analyze, and disseminate technical data on the effectiveness of such products. This web page provides information for manufacturers on how to have a device evaluated, along with information for consumers interested in such products.
IMPORTANT REMINDER: EPA does not approve, certify, endorse, or register any products that pass through this voluntary evaluation program. Neither does EPA approve, certify, endorse, or register any independent laboratory or the test results from any independent laboratory. Any claims by a manufacturer to the contrary are false.

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 (PDF)

Motor Home Gas Mileage Ultimate Guide:       https://topnotchoutdoor.com/motorhome-gas-mileage/. 


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, manufacturers must report the chemical composition 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:

Alphabetical listing of EPA Registered Gasoline Additives:  http://www.epa.gov/otaq/fuels/registrationfuels/web-gas.htm

Alphabetical listing of EPA Registered Diesel Additives:  http://www.epa.gov/otaq/fuels/registrationfuels/web-dies.htm


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:

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, Office of Enforcement www.epa.gov/compliance/resources/policies/civil/caa/mobile/vehicleengine-penalty-policy.pdf (PDF) (33 pp, 1.4M, January 16, 2009).  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.

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 (PDF) (33 pp, 1.4M, January 16, 2009) .  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.






    Copyright © 2003   All rights reserved.   Revised: 04/03/22.                                             Web Author, David Biggs
The information presented on this web site is for information purposes only. Should you decide to perform experiments or construct any device, you do so wholly on your own responsibility
-- Neither the company hosting this web site, nor the site designer author are in any way responsible for your actions or any resulting loss or damage of any description, should any occur as a result of what you do.