Abstract-LPGThe study showed that the highest useful pressure of LPG is 10.5: 1 while natural gas was 13: 1. When adding natural gas to LPG, the compression ratio can be increased to a certain limit to be the highest increase in the mixing ratio of 80% with a compression ratio of 11.6: 1. The natural gas has a low flame propagation speed so the spark timing should be provided when added to the LPG. The addition of this addition reduces the induced power at a low speed due to this natural gas characteristic. Natural gas reduces the engine's output power by reducing the engine's volumetric efficiency by entering the combustion chamber with its gas phase.