Balancing the demand for high thermal efficiency with strict NOx emission limits remains a persistent dilemma in modern diesel engine development. This study explores a potential solution by investigating how hydrogen enrichment interacts with EGR in a diesel dual fuel engine with constant load. Instead of treating these variables in isolation, we employed a randomized full factorial design to map their simultaneous effects, testing hydrogen flow rates up to 7.5 LPM and EGR levels up to 15%. Through rigorous statistical analysis (ANOVA and Tukey’s HSD), we uncovered a distinct "sweet spot" in engine operation. While hydrogen injection successfully boosted thermal efficiency and cut fuel consumption due to its rapid combustion, it expectedly triggered a spike in NOx emissions. However, our analysis revealed a crucial interaction: adding 10% EGR effectively neutralized this emission penalty without severely crippling the engine's power. Interestingly, we also identified a saturation point at 7.5 LPM of hydrogen, where the engine ceased to gain further efficiency due to volumetric losses. Ultimately, the data suggests that pairing 5.0 LPM of hydrogen with 10% EGR offers the most balanced configuration restoring power to baseline levels while keeping emissions in check.