# Strategies for Reducing Automobile Fuel Consumption
## 3 Vehicle Design and Technology
### Improved Fuel Economy of Vehicles by Reducing Friction Losses
A particular focus is given to the predominant contributors to these losses, including the piston-ring/cylinder assembly and various drivetrain components. The distribution of energy consumption, including frictional losses, of a medium-sized passenger car is detailed in Table 1[44]. Moreover, understanding the intricacies of bearing tribology and valvetrain dynamics is crucial in addressing these losses. These components can significantly affect overall vehicle efficiency under different operational conditions. The multifaceted nature of mechanical losses is related to various factors such as lubricant quality, thermal conditions, and material properties. Furthermore, it is crucial not to overlook the auxiliary components, as they can account for 20% (or more) of the mechanical friction losses [45]. Initiatives have been undertaken to reduce _boundary-type_ lubricated friction in bearings and other tribological systems in ICEs. A notable example includes the incorporation of friction-reducing additives into engine lubricants, such as molybdenum dithiocarbamate (MoDTC) [46]. On the other hand, the _valvetrain_ presents a diverse array of tribological challenges. Its complexity includes several tribological interfaces: cam/follower, valve-guide/stem-seals, valve-heads/valve-seat, and other tribological systems, such as hydraulic lash adjusters, lifter guides, pivots, camshaft bearings, and both belt and chain drives. Refinement of these components can help ensure the valvetrain's efficient functionality. The dual objectives of obtaining more sustainable designs of vehicles and (specifically) the development of stringent regulatory standards advocating for efficient engines with augmented power-to-weight ratios require tribological components to operate at the minimum oil film thickness. A prevailing trend leans toward the adoption of engine oils with lower viscosities, such as SAE 5 W-20 and 0 W-20, targeting enhanced fuel economy. While \begin{table}
\begin{tabular}{c c c} \hline \hline
**Energy Distribution** & **Description** & **Percentage** \\ \hline Fuel Energy Propelling Wheels & In urban driving cycle & 12\% \\ \hline Mechanical Losses (predominantly friction) & In urban driving cycle & 15\% \\ \hline Fuel Consumption Reduction & From reducing mechanical losses & 1.5\% per 10\% reduction in mechanical losses \\ \hline Frictional Losses in Engine & Proportion of engine’s energy consumption & 48\% \\ \hline Acceleration Resistance & Proportion of engine’s energy consumption & 35\% \\ \hline Cruise Resistance & Proportion of engine’s energy consumption & 17\% \\ \hline Piston Ring/Cylinder Assembly and & Proportion of total frictional losses & 66\% \\ Bearings Friction & & \\ \hline Valvetrain, Crankshaft, Transmission, & Proportion of total frictional losses & 34\% \\ \hline Valvetrain Friction & Proportion of mechanical losses & Averages around 10\%, up to 20–25\% at lower engine speeds \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Energy distribution and frictional losses in a medium-sized passenger car. this strategy reduces frictional losses, it also raises concerns regarding engine longevity, accentuating the importance of the surface technology in engine components in relative motion. These lubrication intricacies underscore the necessity of consistent oil replacements and the utilization of premium engine oils, which are formulated as a response to the requirements imposed by diverse driving scenarios. In this regard, appropriate maintenance protocols serve to anticipate problems stemming from degraded oil, safeguarding the engine from potential wear and corrosion. The tribological community that specializes in engine systems is faced with a substantial challenge when trying to reconcile the complex tribological effects affecting engine components with the (also) complex chemical interactions and degradation processes exhibited by engine lubricants, both in their fluidic state and on component surfaces.