Compressed Natural Gas Motor Vehicle Fuels

This page last reviewed on February 20, 2018


Compressed Natural Gas (CNG) is a gasoline and diesel fuel alternative consisting primarily of methane. The gas is associated with other fossil fuels (coal or oil) and is created by methanogenic organisms in landfills. The gas is extracted from the source and compressed to a high pressure where it can be stored in a vehicle fuel tank.

Recent Activities

July 2014

Work Continues on Revisiting the CNG/LNG Specifications

Staff is currently examining two ongoing studies.  The first is the Effect of Natural Gas Fuel Composition on Vehicles study, which is being conducted by the University of California at Riverside.  This study is sponsored by ARB and the California Energy Commission (CEC) to review the emission effects that lower Methane Number and higher Wobbe Index gas supplies may have on light and heavy-duty engines.  The second is the Tool for EMission Processing of LNG Expansion Scenarios (TEMPLES) study, which the University of California at Irvine (UCI) is conducting. This study is a predictive model used to estimate changes in GHG and criteria pollutant emissions from mobile and stationary sources. We anticipate that these studies, along with additional information we are gathering in collaboration with the gas companies, air districts, and other stakeholders, will enable us to better evaluate alternatives to the current set of CNG motor vehicle fuel specifications in California.  We intend to schedule public workshops in 2015 to discuss regulatory concepts and other proposals based on these developments; the goal would be to propose a rulemaking for our Board’s consideration in late 2015.

Converting Vehicles to Compressed Natural Gas Fuel

Individuals interested in converting gasoline or diesel vehicles to operate on an alternative fuel must ensure that the alternative fuel retrofit systems have been certified by ARB. For more information on converting a vehicle to run on compressed natural gas fuel, and for the list of certified retrofit systems for various vehicle makes and models, please visit ARB's web page that covers  Certification of Alternative Fuel Retrofit Systems.

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Contact Us

  • For more information about the Compressed Natural Gas Motor Vehicle Fuels, please contact Linda Lee at (916) 322-1521.