Car engine oil Vision by Petronas of one liter, with a viscosity grade of 15W-40.

Car oils are important for the proper functioning of the engine and provide lubrication and protection against wear to its moving parts. Additionally, they remove heat, keep the engine clean, and improve its performance. However, the choice of the appropriate oil depends on various factors, such as the type of engine, driving conditions, and specific specifications set by the car manufacturer.

The numbers on car oils indicate how thick or thin the oil is at different temperatures and are represented by 2 numbers: the first with the letter "W" (Winter), refers to the oil's fluidity when the engine is cold, while the second number refers to its fluidity when the engine operates at high temperatures.