1. Short title This Act may be cited as the Fuel Choice and Deregulation Act of 2018 . 2. Alternative fuels (a) Aftermarket conversions of motor vehicles to alternative fuel Section 203 of the Clean Air Act ( 42 U.S.C. 7522 ) is amended by adding at the end the following: (c) Older vehicles (1) In general The aftermarket conversion of a motor vehicle to alternative fuel operation shall not— (A) be considered tampering under this section if the aftermarket conversion system manufacturer or the person performing the conversion demonstrates that the development and engineering sophistication of the conversion technology is— (i) matched to an appropriate motor vehicle or group of motor vehicles; and (ii) well-designed and installed in accordance with good engineering judgment so that the aftermarket conversion system does not degrade emission performance, as compared to the performance of the motor vehicle or motor vehicles before the conversion; or (B) require the Administrator to issue a certificate of conformity. (2) Label The person performing a conversion described in paragraph (1) shall affix a label to the motor vehicle stating that— (A) the motor vehicle has been equipped with an aftermarket conversion system