Several high-speed diesel engine test runs were carried out during 2010 in Aalto University using a single-cylinder research engine. The main focus was on miller cycle and exhaust gas recirculation (EGR) tests using hydrotreated vegetable oil (HVO) as fuel. But also reference tests were run using both HVO and regular EN590 diesel in normal engine configuration and running parameters.The miller tests included a sweep of three different intake valve closing timings and also a sweep with advanced start of injection. The results showed a reduction in both nitrous oxides (NOx) and smoke emissions.EGR tests showed a significant decrease in NOx emissions as was expected. The lower smoke emissions of HVO compared to EN590 enable higher EGR percentages with similar PM emission and hence bigger NOx emission reduction.