Vehicle and Engine Alternative Fuel Conversions
On this page:
- Overview
- How to submit information to EPA to demonstrate compliance
- Lists of EPA-compliant conversion systems
Overview of Conversions
Consumer Information
If you are interested in modifying your vehicle or purchasing a modified vehicle, see:
For general information, see:
- Green Vehicle Guide's: Alternative vehicle fuels
Conversion systems modify vehicles and engines so that they can run on different fuels than the ones for which they were originally designed.
Any change to the manufacturer’s original vehicle or engine design is a potential violation of the Clean Air Act and can cause problems, including increased emissions.
- Clean Air Act prohibition: 42 U.S.C. §7522(a) — Refer to sub-section (3)
Therefore, EPA has established protocols through which conversion manufacturers can demonstrate that:
- Emission controls in the converted vehicle or engine will continue to function properly; and
- Pollution will not increase as a result of conversion.
These protocols are conveyed through the following rules and guidance:
Applicable Regulations
Related Guidance Letters
- Updated Assigned Deterioration Factors for Alternative Fuel Converters (pdf) (5 pp, 56 KB, CD-12-07(Revised), March 30, 2012)
- Updated Certification Guidance for Fuel Converters (October 2010) (pdf) (13 pp, 308 KB, October 2010)
Includes guidance on whether conversions to full battery electric require alterative fuel vehicle certification. - Updated Certification Guidance for Fuel Converters (February 2006) (pdf) (22 pp, 150 KB, CISD-06-02[LD-AFC], February 3, 2006)
Provides information for small volume manufacturers who convert vehicles and engines to operate on alternative fuels.
How to Submit Information to EPA to Demonstrate Compliance
EPA's Final Rule for Clean Alternative Fuel Vehicle and Engine Conversions spells out processes through which conversion manufacturers may demonstrate compliance with vehicle and engine emissions requirements. The processes differ depending on the age of the vehicle or engine to be converted.
There are three age-based demonstration categories:
- Conversion systems to be used on new and relatively new vehicles/engines;
- Conversion systems to be used on intermediate-age vehicles/engines; and
- Conversion systems to be used on outside useful life vehicles/engines.
The following information summarizes the requirements. Regulated parties should always refer to the regulations for compliance purposes.
Conversion Systems to be used on New and Relatively New Vehicles
The compliance demonstration for conversion systems intended for use on new vehicles and engines is a certification process similar to the original engine manufacturer certification process. Use the applicable link below.
- Certification and fuel economy for passenger vehicles (light-duty)
- Certification for commercial trucks and buses (heavy-duty)
Conversion Systems to be used on Intermediate Age and Outside Useful Life Vehicles
The compliance demonstration for conversion systems intended for use on intermediate age and outside useful life vehicles and engines is described in regulations and guidance. Please follow the link provided below for information about how to submit the applicable templates and information:
Lists of EPA-Compliant Conversion Systems
Once a manufacturer has demonstrated compliance, the conversion system will appear on the applicable list: