How can the engine oil save fuel?

High-quality engine oils can considerably reduce costs for fuel. How does this occur? A considerable part of energy is used to overcome friction resistance of interacting engine parts. Use of high-quality engine oils in the engine considerably reduces the friction resistance. As a result, less energy is lost and this guarantees the increase in the efficiency factor. Therefore, less fuel is spent. Such oils are called energy-saving, for example, 5W-40 Energy Vamp, 5W-30 Drive Vamp.