Final answer:
The efficiency of a car engine with a power output of 100 kW, based on typical automobile engine efficiency, is 25%. This indicates the proportion of energy input that is converted into useful work.
Step-by-step explanation:
The efficiency of an engine can be defined as the ratio of useful energy (work) produced to the total energy input into the system. Given that the car engine in question has a power output of 100 kW, and based on the information that a typical automobile engine has an efficiency of 25%, we can conclude that the efficiency of this specific engine is also 25%. This percentage expresses how much of the energy supplied to the engine is actually converted into work versus how much is lost, generally as heat.