Compressed Natural Gas has been an efficient means of propulsion since the '60s and typically involves Natural Gas that has been compressed up to 3,600 Psi for storage and fuel.

Cummins Westport is the Compressed Natural Gas division of Diesel Engine Manufacturer Cummins Inc. Formed in a Merger between Westport Innovations and Cummins, Westport Innovations is a Canadian developer and refiner of alternative fuels including CNG and LNG technologies. Westport Innovations is best known for pioneering standard Diesel Engines to run on CNG without altering the combustion chambers. Cummins begain to sell CNG engines shortly after this merger in 2013.

Cummins Westport offers 4 Diesel CNG alternatives:

The Cummins ISX12G is a CNG that provides a higher amount of displacement than most other CNGs. Because of this it is one of the most widely used CNGs for Class 8 trucks and is used by Kenworth, Peterbilt and Freightliner in their line up.

The 8.9 L Cummins ISL G is the most widely used CNG for medium duty trucks and for School and Transit buses. It is Cummins' most successful CNG to date as most carriers choose this engine to save on operating costs.

Due to a revision in a 2010 EPA mandate the C Gas plus is no longer built for the North American market. The C Gas plus is still offered to European customers. The C Gas Plus was the most widely used Cummins CNG for Hybrid applications because it provided an unusually strong torque ratio.

As with the C Gas Plus the B Gas Plus is no longer offered in North America due to an EPA mandate revision.

Cummins Conversion Kits allow operators of buses and trucks with older engines to "Refurbish" or "Rehab" them into new engines using CNG.