In this study, a single-cylinder research engine was refitted to CNG fuel usage. The effect of CNG fuel on the engine performance was examined in detail in different engine loads and speeds. In the single-cylinder test engine, the CNG fuel was injected to intake manifold through the suction time. Performance measurements showed that the effective power increased through the increase of the engine speed. The specific fuel consumption decreased as the load increased, but it was seen to increase with the engine speed increase. Similarly, it was seen that while the volumetric efficiency was about 80% at the low speed, the efficiency rate fell to 65% as the engine speed increased. As a result, the specific research engine at a compression ratio of 10 was run with CNG fuel, the performance curves were obtained, and performance analysis was carried out successfully. in the case of CNG usage, the results showed that as the engine speed increased volumetric efficiency decreased and the fuel consumption increased.