The aim of the study was to determine impact of commercially available hydrotreated vegetable oil (HVO) and its mixture (HVO5, where 5% (v/v) HVO and 95% (v/v) FDD) with diesel fuel (FDD) on the power, torque, fuel consumption, and exhaust gas composition of an atmospheric internal combustion diesel engine used in off-road applications. Diesel fuel was used as the comparative fuel. Testing was realized in a full-load mode on the KOHLER KDI 1903 M 3-cylinder diesel engine on a SIERRA CP-Engineering engine test bench. The AVL SESAM FTIR exhaust gas analytical system was used to determine exhaust gas emissions, while the AVL KMA Mobile fuel consumption measuring device was used to measure fuel consumption. Research showed that the lowest power and torque readings were obtained with FDD, while HVO showed a slightly higher result compared to the fossil diesel fuel. At the same time, the highest hourly fuel consumption was observed running on HVO5, while the lowest was observed with FDD. Increases in carbon monoxide (CO), carbon dioxide (CO2), and nitrogen oxide (NOx) emissions were observed for HVO5 compared to those of FDD. The CO content in emissions increased by an average of 3.0% using HVO and by an average of 36% using HVO5, but the NOx content in the emissions increased by an average of 3.0% using HVO and by an average of 8.8% using HVO5. The reduction by an average of 60% using HVO in emissions was found in the case of hydrocarbons (HC). Research confirmed that the physicochemical properties of HVO could leave an impact on the main engine performance parameters and exhaust emissions.

Biodiesel is increasingly used as an additive to fossil diesel fuel. For summer periods it is compulsorily in Latvia to use diesel fuel with 4.5-7 % biodiesel fuel mix. Some technical disadvantages of biodiesel/fossil diesel blends are mentioned by many researchers, for example, reduced energy density, and degradation of fuel under storage for prolonged periods. Therefore, one of the solutions might be blending of different biofuels instead of biodiesel. Hydrotreated vegetable oil (HVO) is one of the most promising next generation biofuels in the near future. An unmodified passenger car Opel Insignia 2.0 CDTi (manufactured in 2011) with a four-cylinder diesel engine (power 96 kW) has been investigated. Chassis dynamometer Mustang MD-1750, AVL KMA MOBILE fuel consumption meter, and AVL SESAM FTIR multi-component exhaust gas measurement system were used during the experiments. Running the car with diesel fuel mixed with 7 % of biodiesel, it developed 2.1 % less maximum power and 1.3 % less maximum torque compared with fossil diesel, and about 2.3 % less power and 1.5 % less torque compared to diesel fuel blended with 7 % HVO fuel. Diesel fuel l/7 % biodiesel blend fuel consumption is in average 3.1 % higher compared to pure fossil diesel, and in average 3.0 % higher in comparison with diesel fuel mixed with 7 % HVO fuel. Blend of 7 % HVO with fossil diesel fuel compared to diesel fuel mix with 7 % of biodiesel approximately by 4 % decreases the amount of NO x , by 3 % CO 2 , and about 3.5 times unburnt hydrocarbon content in exhaust gases, but CO increases by approximately 90 %.

All member states of the European Union are bound to the EU directives and regulations on the reduction of greenhouse gas emissions and the use of renewable energy sources in road transport. As the objectives defined in these documents cannot be achieved only by the mandatory blending of biofuels, opportunities to use new generation biofuels in pure form have to be investigated. One of the most promising fuel types in this matter could be hydrotreated vegetable oil (HVO), which can be produced from a variety of non-food raw materials. To determine the effect of fuel on the car's dynamic, economic and environmental performance, experimental studies were carried out using a car model Opel Insignia powered by pure HVO fuel (NExBTL manufactured by Neste Oil) and regular diesel fuel. The tests were performed on a power bench, but the AVL measuring equipment was used to determine the exhaust gas composition and fuel consumption. The experimental results show that the power and torque characteristics in the whole range of engine speed are similar when operated with NExBTL and fossil diesel. The average NExBTL fuel volumetric consumption is about 3% higher, fuel mass consumption 5.3% lower and fuel energy input 4.5% lower compared to diesel fuel. This can be explained by the differences between the physical properties of the tested fuels, such as density, lower heating value and compressibility. Exhaust components, which are usually compared in studies of different fuels, using NExBTL fuel tend to decrease compared to fossil diesel. A reduction was observed in most driving modes tested. Unburned hydrocarbons decreased on average by 44%, SO2by 13.3%, NOx by 5% and CO2by 3.8%. Experimental studies show that NExBTL fuel might compete with fossil diesel in the future. It is confirmed by measurements of power, fuel consumption and exhaust gas content. An important drawback for the wider implementation of this fuel is its production cost.