Cruising Speed (mph) = (Engine Displacement in Litres) * 20 + 10
For example, a car with a 2.0-liter engine would have a right cruising speed of (2.0 * 20) + 10 = 50 mph.
This formula is based on the assumption that the car is operating at a steady speed on a level road with no traffic. Factors such as hills, wind, and traffic can affect the optimal cruising speed.
Additionally, this formula is just a general guideline, and the actual optimal cruising speed may vary depending on the specific vehicle and its performance characteristics.