Major shipping companies utilize fuel oil additives to reduce fuel costs and to comply with emission regulations. Although the use of fuel additives for marine heavy fuel oil has increased dramatically, their effects on performance have not been verified. This study investigated the effects of fuel additives, not only at the scale of the engine test bed but also through chemical laboratory tests. Fuel separability tests were conducted to evaluate fuel oil stability. The results indicated that there was improved stability with certain dosages of fuel additives. Fuel combustion and ignition characteristics were evaluated via a Fuel Combustion Analysis (FCA) test, which showed that combustion parameters, including the pressure trace and rate of heat release (ROHR), were significantly affected by the use of fuel additives. The ROHR results showed modified performance indicators, particularly in regard to the position of the ROHR, ignition delay, end of main combustion, and end of combustion. The testing only aimed to determine the tendency at low engine loads, because engines typically operate at low loads within emission controlled areas. The engine test results showed that some additives were associated with reduced fuel consumption, but that some resulted in higher specific fuel oil consumption levels than those for fuel oils without additives. Nitrogen oxide (NOx) and particulate matter (PM) emission characteristics were also investigated, and data revealed that fuel additives affected the emission components. (C) 2016 Elsevier Ltd. All rights reserved.