The search for alternative fuels for diesel engines is being explored due to rising oil prices and increasing vehicle emissions. Due to its low cost and properties, natural gas is considered a suitable option for diesel engines. However, the costs required for research and misleading experimental setups can lead to time loss for researchers. Therefore, conducting computer simulations before experiments can reduce costs and provide faster access to desired data. Nonetheless, these simulations need to be compared with real experimental data. Hence, the study consists of two phases. In the first phase of the study, experiments were conducted with diesel fuel. Subsequently, a one-dimensional combustion model was developed in the AVL BOOST program. The established model was validated by comparing it with experimental data. Once the validated model was obtained, performance, emissions, and combustion analyses were carried out by adding different proportions of CH4 (20%, 40%, 60%, and 80%) to diesel fuel using the model in AVL BOOST. As a result of the study, improvements in effective power and effective efficiency were achieved with the addition of varying proportions of CH4 to the engine. Upon examining emitted exhaust emission values, it was observed that NOx emissions increased while CO emissions decreased.