Abstract: This research is concerned with investigations switching the conventional fuel (gasoline) by an alternative fuel and on lowering the concentration of toxic components in combustion products. LPG as an alternative to gasoline has emerged as a solution to the deteriorating urban air quality problem, especially in an oil country like Iraq. An instrumented experimental setup is prepared to conduct practical tests of various operating parameters such as Brake specific fuel combustion, brake power, brake thermal efficiency, volumetric efficiency engine speeds, air fuel ratio in cylinder pressure, exhaust gas temperature, CO, CO , CxHy, O and 2 2 NOx. Concerns have been prepared for better understanding of operating conditions and constrains for LPG fueled internal combustion engine. The obtained experimental results revealed that LPG fuel improves the brake specific fuel consumption and brake thermal efficiency but reduces the brake power compared to gasoline fuel operation, the maximum of percentage deviation BSFC in gasoline fuel compare with LPG fuel reported is 3.11% for engine brake power equals to 10 kW when compression ratio equal 9.9:1. The maximum cylinder pressures predicted for LPG are lower than that produced by gasoline fuel which causes no damage to engine structural elements. LPG reduces the engine volumetric efficiency compared to that produced by gasoline fuel, so, engine effective power is decreased, the maximum volumetric efficiency in all cases is reached at 3500 rpm and for equals to 10 kW. The volumetric efficiency was 76.8% for LPG and 85.9% for gasoline when compression ratio equals to 9.9:1. Compression ratio and equivalence ratio have a significant effect on both performance and emission characteristics of the engine and have to be carefully designed to achieve the best engine performance characteristics. The equivalence ratio is higher for gasoline than LPG because the first has higher BSFC due to increase in actual air-fuel ratio required for combustion, that inversely proportional with the equivalence ratio. In a general behavior the exhaust gases temperature increases with increasing engine speed, compression ratio and brake power for both fuels. For the same brake power and engine speeds, it is found that exhaust gas temperatures for gasoline fuel be higher at all engine speeds compared that for LPG fuel, the maximum exhaust gas temperature reported is 706°C for LPG fuel while that for gasoline is 741.4°C at point 1 for brake power on engine equals to 10 kW and compression ratio equals to 9.9:1. Gas emission of CO, CO , NOx and CxHy with 2 LPG fuel is found lower than that produced by gasoline fuel. O₂ emissions for LPG fuel be higher compared to that produced by gasoline fuel.