What Causes High Oil Pressure in a Car?

Written by katelyn coyne
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What Causes High Oil Pressure in a Car?
High oil pressure is only a minor concern. (exterior gauge image by Neelrad from Fotolia.com)

Oil pressure is determined by the rate at which oil flows through the internal combustion engine of a car. Low oil pressure is a real danger for engines, as it indicates that the bearings in an engine have worn, allowing the oil to flow more easily and at a lower pressure. However, high oil pressure is generally not a concern for motorists. Oil pressure fluctuates with the heat of a machine, and though high oil pressure can indicate a serious problem, it generally means the engine is in an adjustment period.

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Oil Pressure at Idle

For many cars, oil pressure is much higher upon start-up or while idling. The reason for this has to do with the temperature of the engine. When an engine has been sitting turned off, it cools down, as does the oil that flows through the machine. Upon start-up, the engine temperature begins to rise. As it rises, so to must the oil heat up to find a level pressure to flow through the machine. Cooled oil is thicker, causing it to flow more slowly and at a higher pressure through the machine, until it reaches its optimal operating temperature.

Pressure Relief Valve

Recurrent high oil pressure, even after the machine has been running for a while, can indicate a problem with the pressure relief valve. The pressure relief valve is responsible for regulating oil pressure throughout the internal combustion engine. It is a safety device intended to keep vessels or piping from experiencing extreme pressure. When this device is malfunctioning, it will cause high oil pressure in an automobile.

Types of Oil

The type of oil put into an engine can also account for extremes in oil pressure. Low-weight or thin oils will operate with low oil pressure, as they will pass through the machine quite easily. Thicker oil will pass through the machine at higher oil pressure readings. Generally, after an oil change, when fresh oil is introduced into the machine, oil pressure will increase. This, however, is only a sign that the oil that formerly operated your car was too thin for optimal performance.

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