Summary

Allows aftermarket conversions of older motor vehicles to operate on alternative fuels without automatically being treated as emissions 'tampering' if the conversion is properly matched, designed, and installed, and requires a label noting the conversion. Limits the Environmental Protection Agency's authority to regulate "biomass fuel" under the Clean Air Act. Changes fuel-economy law to create new fuel-type definitions, give certain manufacturers credit equivalence for EPA greenhouse-gas rules, extend credit carryforward timing, and add an 8 mpg bonus for qualifying "fuel choice" manufacturers for model year 2026 and later. Also makes small textual edits to existing fuel waiver language.

Key Points

• Aftermarket conversions to alternative fuels are not automatically treated as tampering if matched, well-designed, and properly installed.
• Installers must place a label on converted vehicles noting the aftermarket conversion took place after the original sale.
• EPA retains authority to ban or stop conversion systems that demonstrably worsen emissions.
• EPA is barred from prohibiting or controlling "biomass fuel" under the Clean Air Act language added by the bill.
• New fuel-economy definitions added and a special status for "fuel choice enabling" manufacturers that aligns CAFE compliance with EPA GHG rules.
• Earned fuel-economy credits can be used in any of the five model years after the earning year if not used earlier.
• Qualifying fuel choice enabling manufacturers receive an 8 mpg bonus to their calculated fleet average (applies to model year 2026+).
• Textual edits to ethanol waiver language remove the phrase 'additional alcohol or' and make a minor conjunctive insert.
• No new federal funding or new programs are created; changes work by altering existing regulatory standards and incentives.
• Potential for legal and regulatory disputes over the scope of EPA authority and emissions effects of converted vehicles and biomass use.

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