The elements that determine a vehicle’s fuel efficiency are clear. One of the most critical
determinants relates to engine design (how the engine-generated tractive effort is produced). Engine designs that increase the quantity of air entering the combustion chamber, improve fuel delivery to the combustion chamber, and decrease internal engine friction lead to improved fuel efficiency. Improvements in other mechanical components, such as decreasing slippage and improving the mechanical efficiency of the transmission and driveshaft, also increase the overall fuel efficiency.
In terms of resistance-reducing options, decreasing overall vehicle weight (W) will lower grade and rolling resistances, thus reducing fuel consumption (all other factors held constant). Similarly, aerodynamic improvements such as a lower drag coefficient (CD) and a reduced frontal area (Af) can produce significant fuel savings. Finally, improved tire designs with lower rolling resistance can improve overall fuel efficiency. However, there can sometimes be a trade-off between improved efficiency and safety. For example, low rolling resistance tires may not be able to the same high coefficient of road adhesion values that high-performance race tires can. Possible safety-efficiency trade-offs must be given careful consideration.