Impact of Natural Gas Composition on the Performance and Emission of Heavy/Medium-Duty Natural Gas Vehicles - Phase 2

Natural gas fuel composition can have an impact on emissions for older technology heavy-duty vehicles

University of California, Riverside


Riverside, CA

Recipient Location


Senate District


Assembly District



Amount Spent



Project Status

Project Result

Project completed and final report published on the CEC website.

The Issue

Gas variability poses challenges for natural gas vehicle technologies. Although some vehicle testing has been completed, there is a gap in information about the effects of gas variability on the performance of engine technology exhaust aftertreatment, and ultimately on urban air quality. Higher emissions of air pollutants, such as oxides of nitrogen (NOx), are precursors to ozone. California is largely not in compliance with federal standards for ozone, and the ARB and air districts are spending considerable resources to find ways to reduce ozone pollution. Increases in NOx emissions from compressed natural gas vehicles will exacerbate air quality.

Project Innovation

This project evaluated the impact of various NG compositions on the performance and emissions of NG powered heavy- and medium-duty vehicles, including identifying and obtaining vehicles/engines to test, selecting natural gas blends to test, obtaining gases, testing and data analyses. Testing addressed issues such as the impact of the different LNG blends on fuel economy, operability and emissions of air pollutants. The results showed that fuel composition, engine operating conditions, and driving cycle had effects on the formation of exhaust emissions from all the older heavy-duty vehicles.

Project Benefits

Environmental Benefits:
This study has shown how exhaust emissions of older engines and newer stoichiometric engines differ when run over a variety of duty cycles and under different operating conditions. The evaluation of the p

Key Project Members

Project Member

Thomas Durbin



Mark Wilson


Contact the Team