What is actually meant with lubricate. In principle, a substance is brought between two with different speed moving components, the otherwise touch each other and could cause particularly wear-prone friction. The distance between the two friction partners is thus just so wide that lubricant with suitable viscosity fits between.

Now there is very highly viscous lubrication, e.g. by lubrication grease and low-viscosity by oil. The latter must constantly be added respectively replaced, the former only infrequently. There is therefore the term 'central lubrication', which in the area of trucks and construction machines is of particular importance. One of the last in the car can be found, for example, in the Mercedes 300 S from 1951. By the way, is being or has been centrally lubricated with normal grease, liquid grease or oil. Unfortunately, the residues end up ultimately in the environment, which is why manufacturers advertise that they help to reduce the amount of residues (Video 1). We remain at the bearings lubricated by oil. Did you know that the oil circulation in the engine is relatively independent of the engine speed?

When the oil from the outer main bearing shell of the crankshaft enters into the intermediate space, then is opposed to a with the rotational speed increasing centrifugal force. A similar effect is possible in the connecting rod bearings. Especially with modern controlled pumps must be secured the transport of oil down to the last bearing e.g. the camshaft. The oil circuit must moreover increasingly taking on tasks of control. Just consider various adjustment options on camshafts, valves and e.g. belt tensioners.

The necessary cooling by the oil circuit relates to the created warmth by combustion and friction, which is emitted to the coolant. The former can be very effectively facilitated by nozzles at the bottom of the cylinder. It is to consider here a guided jet always with the same distance from the cylinder wall, which hits guaranteed the relatively small opening to the annular channel of the piston in each of its positions, unlike the Video 2, in which only the piston crowns are injected from the inside. The temperature of the engine oil is in contrast to the encircling amount of oil indeed dependent of the engine rotational speed.

So if certain minimum pressures from just under 1 to about 4.5 bar are required depending on the operating state, it is based on relatively high oil temperatures, occurring in practice. One is thus on the safe side thereby. Regulated pumps can save here in many operating states, more than half of the drive energy, opposite to the working always evenly up to the opening of the pressure limit. This is especially true for two-stage pressure-regulated pumps. 11/15