The effects on engine emissions resulting from the addition of oxygenated additives to the fuel, have been investigated using a low emissions, Detroit Diesel Corporation (DDC) Series 60 engine. The oxygenates evaluated were selected on a combined basis of their fuel blending properties and potential costs. Oxygenates of varying molecular structures were selected for evaluation. The test results show that particulate emissions are directly related to the concentration of oxygen in the fuel. The particulate reductions are accompanied by small increases in NO, emissions. In general, the addition of an oxygenate to the fuel reduces carbon monoxide and hydrocarbon emissions. Non-regulated aldehyde and ketone emissions are also reduced with the addition of an oxygenate. When a peroxide-based cetane improvement additive was added to the oxygenated fuel, an emission profile similar to that from a low aromatic fuel was obtained. The combined use of an oxygenate and a peroxide based cetane improver offers a potential alternative to produce a fuel with an emissions profile acceptable for use in California.