Regulated and unregulated emissions from two Euro 6b diesel passenger cars tested using three different blends of hydrotreated vegetable oil (HVO), fossil diesel and commercial diesel (B7) were investigated at 23 degrees C and -7 degrees C using the World harmonized Light-duty vehicle Test Procedure at the Vehicle Emission Laboratory of the European Commission Joint Research Centre Ispra, Italy. The HVO blends used were: Neat HVO (100 vol% HVO), 30 vol% HVO and 7 vol% HVO. One of the vehicles was also tested using the three HVO blends on-road following a RDE compliant route. Overall, the use of different HVO blends and diesel did not lead to fuel related trends on the emissions of the tested vehicles in the laboratory nor on-road. However, HVO-100 resulted in similar to 4% lower CO2 emissions than the other fuel tested in all the studied conditions. Low ambient temperature caused an increase of the emissions of studied compounds (with the exception of NH3) with all tested blends. The experimental results showed that in many cases the observed outcomes were probably attributable to a combination of combustion effects, after-treatment effects, and their control strategy.