Oil pressure (technology)

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The term oil pressure refers to two areas in technology. On the one hand, a hydraulic system must have a working pressure appropriate to the purpose (control, pressure lubrication, reaching a certain flow rate). On the other hand, the oil is used for lubrication and at the same time for heat compensation. The latter is not just related to heat engines.

Pascal's principle

Pascal's principle says: If a force acts over an area on an enclosed liquid, a pressure is created that spreads equally throughout the liquid.

The following applies:



The system is only fully operational when a minimum pressure is reached. In more modern machines, monitoring is carried out by means of an oil pressure switch and control unit, so that parts of the system are only released when the pressure is available. Older machines only indicate a reduced pressure, if at all, by means of a control lamp.


Lubrication is often necessary at points where moving parts interlock. Oil is used for this because, compared to grease, it can fulfill other tasks, such as washing away abrasive particles and removing local heat. The oil pressure system consists of channels (lines, bores), lubrication points, drip discs, oil cooler , oil pan , oil filter and oil pump . When the machine is started, this system must first be filled before oil pressure can be built up.

The way in which the oil pressure is monitored varies. Either the pressure is displayed on a scale on a manometer or an operating or warning lamp is controlled with an oil pressure switch (oil pressure monitor). Seized shafts, destroyed bearings or piston seizures can be the result of insufficient or insufficient oil pressure.

In the case of heat engines (e.g. internal combustion engines ), high temperatures place increased demands on the lubrication system.


  • Richard van Basshuysen, Fred Schäfer: Handbook Internal Combustion Engine Basics, Components, Systems, Perspectives. 3rd edition, Friedrich Vieweg & Sohn Verlag / GWV Fachverlage GmbH, Wiesbaden, 2005, ISBN 3-528-23933-6