The increase in interest in the use of CNG in commercial fleets, especially in heavy vehicles, has been driven by the differential in fuel costs. Traditionally, the price of CNG for transportation applications has followed the trend of the prices of conventional petroleum fuels in the transportation market, with slightly lower prices. The natural gas consumed in the United States of America is produced mainly in the own country and technological advances have increased the potential of domestic supply, while oil imports are affected by the instability of world events. This has caused the price of CNG at the pump to stabilize while the prices of conventional fuels have risen; for some periods of time producing large cost differences between CNG and diesel

This price differential will fluctuate over time, but oil and natural gas supply and market trends make it likely that it will continue to be less expensive to run a CNG vehicle than a diesel vehicle.

The environmental and economic benefits of CNG vehicles, as well as their "green" image, have convinced several large companies with national fleets to implement CNG vehicle programs

However, fleet operators should consider whether the CNG vehicles available on the market fit their needs and whether they will use enough fuel to amortize the costs of the vehicle which are normally higher than diesel, or gasoline vehicles, equivalent.

The fuel cost differential between natural gas and diesel is expected to rise further as the economy recovers because oil supply-demand fundamentals have not changed.