Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Environmental impact-minimizing vehicle tuning refers to the modifying of cars to use less energy. Hybridization: change to a hybrid electric vehicle. One can use an aftermarket kit for the powertrain or use a hybrid adapter trailer. Modifying key engine-selection parameters in the Battery Management System of a hybrid vehicle. Vehicles as mild hybrids have a parameter for the threshold speed on which the vehicle is to switch from electric propulsion to the internal combustion engine. Introducing a higher speed as a parameter can reduce emissions and increase fuel efficiency.