An engine assembly is provided. The assembly includes an internal combustion engine of the type having a air intake manifold and a fuel injector in fluid communication with a cylinder head of the engine and a gasoline or diesel fuel source, a supply line in communication with each channel of the air intake manifold and being in communication with a gaseous fuel source, the supply line further defining an adapter for controlling flow of gaseous fuel therethrough, and a control module for controlling the fuel injector and a valve, the control module being configured to enable the fuel injector when the engine is operating at a first predetermined operation condition and configured to enable the valve when the engine is operating at a second predetermined operation condition. A method of controlling the same is provided herein.