A novel way of using low-cetane-number petroleum gases in a compression ignition (CI) engine is introduced, by directly injecting blends of such fuels with dimethyl ether (DME), a high-cetane-number alternative fuel for low soot emissions. This method both extends advantages of DME and complements its deficiency. Although DME mixes with most hydrocarbon fuels in any ratio, in order to demonstrate the feasibility of the new method and facilitate the analysis, DME-propane blends were investigated in a direct injection CI engine. Some findings of the study are listed.In the engine operated by DME and propane blends, there was no need for significantly increasing the complexity of the fuel system than that employed in the use of neat DME. For the same reason, this method eliminates or minimizes cumbersome hardware necessary when the said gaseous fuels are separately introduced in CI engines.When the content of propane was increased, which accordingly increased the heating value of the blend, the start of injection lagged, and self-ignition became sluggish itself, which resulted in a delayed start of heat release.When the engine load was low, the more the propane content, the higher the specific fuel consumption and the greater the emissions of unburned hydrocarbon. This was interpreted in terms of an over-mixing due to rapid vaporization of propane out of the blend to diffuse and also low combustion chamber temperatures.Mentioning other emissions with the DME-propane blends, soot emission was negligible, and the specific NOx emission was in general lower than with neat DME, which decreased with an increase in both the propane content and engine load.