A fuel formulation having a derived cetane number of at least 35 includes a petroleum fraction and a polyoxymethylene dimethyl ether (OMEx) oligomer mix. The petroleum fraction includes a naphtha fraction with a boiling point in the range from 30° C. to 178° C. The polyoxymethylene dimethyl ether oligomer mix has the general formula H3CO—(CH2O)n—CH3 in which n is between 2 and 7, inclusive. A related method for reducing emissions in a compression-ignited engine includes preparing the fuel formulation having a derived cetane number of at least 35 and combusting the fuel formulation in the compression-ignited engine in place of a diesel fuel, thereby reducing emission of at least one of NOx, CO2, or particulates from the compression-ignited engine.