Vehicle Conversion Basics

Photo of a Ford Transit Connect converted to run on compressed natural gas.

A Ford Transit Connect converted to run on compressed natural gas.

A converted vehicle or engine is one modified to use a different fuel or power source than the one for which it was originally designed, such as converting a diesel vehicle to run on propane, natural gas, or electricity.

Dedicated, Bi-Fuel, and Dual-Fuel Conversions

Vehicles and engines can be converted to "dedicated" configurations, meaning they operate exclusively on one alternative fuel. They can also be converted to "bi-fuel" configurations that have two separate tanks—one for conventional fuel and another for an alternative fuel. Either fuel can be accessed by flipping a switch. Although EPA regulations refer to bi-fuel configurations as “dual-fuel,” the term dual-fuel typically refers to another type of configuration where two fuels are used for ignition. For example, a heavy-duty natural gas vehicle that uses a small amount of diesel for ignition assistance.

Conversion Systems Installation

When you purchase a light-duty alternative fuel vehicle through a dealership, the conversion system is installed by the system manufacturer or by a qualified system retrofitter (QSR), also referred to as a qualified vehicle modifier (QVM). Both have met strict requirements in order to convert OEM vehicles. When converting an in-service vehicle, the work should always be completed by a technician associated with a QSR/QVM, also referred to as an upfitter or installer, who is associated with a manufacturer and holds all relevant emissions-related certifications, tampering exemptions, and permissions.

Converting, retrofitting, or repowering a vehicle can result in long-term return on investment while helping fleet managers achieve sustainability goals. To learn about technology options and considerations for fleets pursuing these options, as well as best practices for selecting and working with project partners, service providers, and reputable vendors, see the report What Fleets Need to Know About Alternative Fuel Vehicle Conversions, Retrofits, and Repowers.

To learn more about code requirements, conversion technologies, and installation practices for propane conversions, the Railroad Commission of Texas has developed a four-part series on converting vehicles to propane. The materials were developed under a Clean Cities American Recovery and Reinvestment Act Project Award and provide technical training on retrofitting, servicing, and fueling propane-powered vehicles.