Due to air pollution and global warming being very actual problems, the regulations demand increasingly stringent targets in terms of CO2 and pollutants emissions reduction. The main way to achieve less CO2 production is to improve the fuel economy of the vehicle, and diesel engines are usually more fuel-efficient compared to spark-ignited engines. Modern diesel engines are equipped with Diesel Oxidation Catalyst (DOC) to oxidize hydrocarbons and carbon monoxide, Diesel Particulate Filter (DPF) to reduce particulate matter emissions, and Selective Catalytic Reduction (SCR) to reduce NOx emissions. Such after-treatment components require proper temperatures in order to work effectively in reducing emissions.