Cetane is a measure of ignition quality for diesel fuels. Higher cetane fuels tend to increase power output and engine efficiency, start easier (especially in colder temperatures), and reduce exhaust smoke and odor. The cetane test is appropriate for diesel, biodiesel, and diesel/biodiesel blends. The D2699 and D2700 RON/MON Octane determination is the appropriate ignition quality test for gasoline-based fuels.