AS9120B, ISO 9001:2015, and FAA AC 0056B ACCREDITED

Different Oil Gauges and How to Read Them

Oil pressure gauges are common to countless vehicles like automobiles and aircraft, serving to convey the amount of engine oil that is present within engine systems. Oil gauges conduct readings in terms of pressure, and they are extremely important in the early prevention of engine malfunctions and breakdowns as a result of poor oil quantities or conditions. As there are various types of oil gauges present in differing vehicles, it is important that pilots, drivers, and operators understand how to correctly read their measurements.

For modern vehicles that have electronic components and displays, the oil gauge will typically be powered through electricity, that of which is supported by a system of wires. By sending a current flow through a coil and determining the resistance value exhibited in the return wire, the oil pressure can be found. Due to the ease of installation that electric oil gauges provide, they have become extremely common for most modern circuits that are present within newer cars and aircraft.

While electric oil pressure gauges rely on the use of wires for conducting their readings, mechanical oil pressure gauges utilize a system of pipes. To conduct a pressure measurement, the mechanical oil pressure gauge will have oil funneled into small pipes at the same time as standard flow into the engine. Additionally, the funneled oil is also supplied to the gauge pipes at the same pressure. This allows for a very accurate reading to be obtained, making mechanical gauges a favorable option for many engineers. Despite this, it is important to be aware of the potential risks associated with oil gauges that stem from their design and construction. If the oil pipes of the mechanical pressure gauge were to become damaged or punctured, oil may have the chance of spewing out of the system at a very high pressure. As this can be a hazardous condition that may put those surrounding the instrument in danger, mechanical gauges must be regularly inspected and maintained.

When an oil pressure gauge is placed on a dashboard or flight deck display, it will often have the appearance of a standard indicator. However, the oil pressure gauge will typically differ from other instruments in the fact that it will often have “OIL” written on the display and present numbers on a scale of 1-100 or 1-80. For mechanical gauges, the display will be a conventional dial and indicator needle that points towards values. If a particular gauge is devoid of any numbering system, it will then most likely have the needle pivot to values between “L” and “H,” those of which indicate low and high pressure. If you require details on what a safe baseline reading is, one should always take advantage of the specific owner’s manual of their automobile or aircraft.

If the gauge is providing you no readings and you are not idling, then there may be an issue. Typically, these stem from a faulty gauge, low oil level, or broken oil pump. For low readings that happen during idling, the gauge should be checked as there may be a drop in oil pressure as a result of a leak or mechanical failure. Lastly, high pressure readings should be a concern if the vehicle has been running for around 30 minutes. Generally, this will indicate a dysfunctional pressure relief valve, oil delivery line blockage, or another issue. When this occurs, the engine should be shut off until the issue is resolved, due to the potential risk of an oil filter burst.

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