Source: Consumer Reports
quote: Turbos allow smaller engines that are more efficient because they have less internal friction, and the reduced weight improves overall vehicle efficiency.
quote: Turbos also produce more lower end torque so the average engine rpm is lowered, also increasing efficiency.
quote: However, the trend is toward regenerative braking which reduces some losses associated with higher curb weight, and better materials, drivetrains, and lubricants have reduced the impact of friction.
quote: High rpm operation loses significant amounts of power to frictional losses and fluid turbulence.
quote: However, the trend is toward regenerative braking