What is an aftermarket alternative fuel vehicle conversion? A converted vehicle was originally designed to operate on gasoline but has been altered to run on an alternative fuel such as compressed natural gas (CNG) or liquefied petroleum gas (LPG or propane). Vehicle conversions offer AFV options to fleet managers and consumers alike, beyond the supply of original equipment manufacturer (OEM) alternative fuel vehicles.

All vehicle conversions must be certified according to Mobile Source Enforcement Memorandum 1A (Memo 1A), as well as the Addendum to Memo 1A, and the Revision to the Addendum to Memo 1A, which were issued by EPA.