The Honda Civic GX is the only car factory-built to run on compressed natural gas (CNG) in the United States available to non-fleet customers.

[3] The GX was manufactured in Honda's Greensburg, Indiana, plant together with the production of conventional Civics from late 2009.

In the 2006 year model, the GX again was equipped with the automatic 5-speed transmission, which improved its fuel economy and extended its range to 250 miles.

The CNG Civic in this market is related to favorable natural gas costs and the numerous high-pressure filling stations.

The promotion of CNG conversions by natural gas producers headquartered in Oklahoma provided an incentive for Honda to market the Civic GX there.

State of Oklahoma incentives were a factor that led United Parcel Service to convert part of their delivery truck fleet to CNG.

The significantly higher compression ratio is usable without detonation due to the 120-octane natural gas that powers the car.

[22] The cylinder containing the high-pressure fuel is carried in the trunk of the car and holds 8.0 gasoline gallon equivalent (GGE) at 3,600 psi (250 bar).

[25] The GX qualifies for high-occupancy vehicle lane (HOV) access in California, Arizona, Utah, and other states.

[28] Honda did not recommend utilizing home refueling options due to possible moisture and chemical contamination of some natural gas supplies.

Honda reserved the right to void the warranty of a car needing service based on inspection of the fuel system for contamination.

[29][30] In 2000 the Civic GX rated first in the "Greenest Vehicle of the Year" list by the American Council for an Energy-Efficient Economy.