<human>:  What is the most efficient way to change the oil in a car?
<bot>: The most efficient way to change the oil in a car is to have the oil drained from the drain plug underneath the vehicle, followed by replacing the old oil filter with a new one. Once the oil is drained, you can then fill the engine with fresh oil of the recommended viscosity for your car's make and model. Lastly, you'll need to replace the drain plug and securely tighten it back on to avoid any oil leakage.