The direct-injection stratified charge engine attempts to incorporate many of the high efficiency features of a diesel into a spark-ignited gasoline engine. Spark-ignition gasoline engines' efficiency is hampered by the fact that engine speed is controlled by "throttling". To slow the engine down, the flow of air into it is restricted, increasing the amount of energy wasted pumping air. The DISC reduces engine speed by decreasing the amount of fuel injected per engine cycle, so throttling inefficiencies are avoided.

To avoid throttling losses, the DISC engine must be able to run "lean" (less fuel per volume of air than a conventional engine). In addition to reducing pumping losses, running lean brings a variety of efficiency advantages, including the ability to increase compression while avoiding engine knocking. Though still not as energy efficient as the diesel, DISC engines with advanced valve controls, high compression and other features offer 15-20% higher fuel economy than typical gasoline engines.

To date, DISC engines have not been offered for sale in the U.S. due to their inability to meet stringent emissions standards. Manufacturers and the U.S. Department of Energy are attempting to develop advanced emissions control systems for "lean-burn" engines in order to make this efficient engine available to American consumers.