Oil tasks (Opel Vectra B)

The oil reduces friction so that the pistons and cylinders, along with all bearing assemblies and the valve mechanism, are subject to minimal wear.

Oil is used for a fine seal between the piston, piston rings and cylinder wall, because otherwise there will be a certain gap between these parts, even if it is only one thousandth of a millimetre. Due to the additional sealing effect of oil, the high pressure resulting from combustion can be transmitted to the piston bases without great losses and converted into energy of movement, and the engine can thus develop optimum power.

Next, the oil is used for cooling. When fuel is burned, only one quarter of the energy obtained can be used to move the car, part of it leaves the engine as heat through the exhaust, and the other part of the thermal energy must be removed by the coolant and oil. For example, the piston can only be cooled by engine oil. First, heat is removed from the piston through the piston rings and sealing oil to the working surfaces of the cylinder and then further into the coolant, second, the oil splashing from all sides in the crankcase cools the piston directly. In addition, each bearing of the crankshaft, camshaft, etc. is cooled by oil. The heat absorbed by the engine oil is removed through the crankcase into the oncoming air flow.

Engine designers have other special requirements for oil: it must not evaporate at high temperatures occurring on the working surfaces of the cylinders. Under such unfavorable conditions, the lubricant film must not break. If it burns, there must be no sediment - in principle, oil consumption means its combustion. Oil must bind soot and dirt so that they do not settle in the engine. It must be resistant to aging and have many other qualities.