© 2022 Elsevier LtdThis study includes the effects of using CNG (natural gas) and gasoline on engine emissions, performance, and lubricating oil in the engine of spark ignition, with boron additive added to engine oil. The experiments were repeated through adjusting boron additive to an engine oil first time when the additive-free engine oil was changed and the engine was at full throttle opening. In addition, the experiment used three different load conditions, at constant 3000 rpm (after 50 h of operation), and used gasoline and natural gas for fuels. The test results showed that from the moment the engine oil was first added, the engine performance decreased as time passed. The decrease in engine performance was less when using boron-doped oil in the engine than when using engine oil without boron. The boron-doped the lubricating oil caused the properties of the lubricating oil to change less with the lower temperature in the engine, apart from the reduction of NOX emissions. Using the boron-doped or the undoped boron engine oil had no effect on emissions by fuel type. Although the use of gasoline fuel in the engine decreased CO, CO2, and HC emissions, NOX emissions increased in the system. The use of natural gas increased CO, NOX and CO2 emissions, but a decrease was obtained in HC emissions. It was revealed that the deterioration in the physical properties of the lubricating oil taken from the engine cartel at different times was less in the boron-doped oil than the undoped boron oil.