Biodiesel is a renewable fuel that can be produced from various feedstocks such as vegetable oils, animal fats and waste cooking oils (WCOs). Biodiesel is an environmentally friendly and sustainable alternative to conventional diesel, derived commonly through the transesterification process from oil of the chosen feedstock (Mosarof et al., 2015). Biodiesel has been widely used in many countries as a blend with conventional diesel fuel to reduce the dependence on fossil fuels, as well as to lower the emissions of greenhouse gases and pollutants. However, the effects of biodiesel blends on real-world exhaust emissions and fuel consumption of diesel vehicles are not well understood and may vary depending on the biodiesel feedstock, blend ratio, vehicle type, engine technology and driving conditions. This article aims to summarize the prevailing knowledge base available regarding the usage of biodiesel blends in real-world studies in the form of vehicle trials.