The paper presents unique research results on the effect of coking of diesel engine injector nozzles powered by mixtures of 10%, 20% and 30% biomethanol and diesel fuel compared to the engine being supplied with pure diesel fuel. The test results, obtained from an experiment conducted in accordance with the ISO 15550-1 standard, show the legitimacy of using biomethanol as an additive to diesel fuel due to the lower coking effect of the injector nozzles, which has a positive impact on the reduction of pollutant emissions during engine operation. Regarding the CEC PF-023 test, the tendency to reduce the coking tendency increases the percentage of biomethanol additive to diesel fuel. With a 10% share of biomethnol, the average coking effect of the injectors is over 1% lower, but with a share of 30% of bio-methanol, the coking effect is nearly 2% lower.

Compressed natural gas (CNG) in dual-fuel diesel engines offers environmental benefits but significantly increases unburned methane (CH₄) emissions, especially at low engine loads. This study investigates the effectiveness of different catalytic converters in methane oxidation under transient test conditions (WHTC). Three types of catalysts (Pt-, Rh-, and Pd-based) were evaluated using a combined approach of empirical engine bench tests and mathematical modelling. The results showed that, under actual exhaust gas temperature conditions, the average methane conversion efficiencies were 3.7% for Pt, 17.7% for Rh, and 31.3% for Pd catalysts. Increasing the exhaust gas temperature by 50% improved the conversion efficiencies to 7.3%, 51.8%, and 69.2%, respectively. Despite this enhancement, none of the catalysts reached the 90% efficiency threshold required to increase the CNG content of the fuel beyond 6% without exceeding emission limits. The results highlight the need for high-activity Pd-based catalysts and optimised thermal management strategies to enable the broader adoption of dual-fuel engines, while complying with Euro VI standards.