How Does an Oil Pressure Gauge Work?

The oil pressure gauge is one of the most important instruments in a car. It acts as an indicator of the engine’s overall well-being and as an early-warning system, giving advance notice of any problems so you can investigate the cause before an expensive breakdown occurs.

How much do you know about your car’s motor oil? You may already know the difference between synthetic and conventional oil and why it’s important to have regular oil changes, but how about your oil pressure gauge? The oil pressure gauge is one of your car’s most important instruments. It serves as an early warning system for all sorts of potentially expensive problems—if only you know how to read it.

What Is an Oil Pressure Gauge?

An oil pressure gauge is an instrument that monitors the oil pressure in your vehicle. This instrument not only tells you how much oil remains in your vehicle, but it is also an indicator of the general health of your engine. For instance, an oil pressure gauge can warn you of an oil pump failure, broken hose, or a leaking gasket. It is important to monitor your oil gauge on a regular basis.

How Does an Oil Pressure Gauge Work?

The gauge monitors the oil pressure in one of the main oilways near to the pump and filter. To do this it has a tapping in the engine block, into which is screwed a sensor (for electric gauges) or an oil pipe take-off (for mechanical gauges).

The sensor for the oil warning light is screwed into the union or T-piece at this point, whether or not the car is fitted with an oil pressure gauge.

Mechanical gauges work by literally forcing the needle around the dial under pressure from the engine. Electric gauges, on the other hand, work by using the sensor screwed into the engine block to produce a variable resistance that affects the amount of current passing through the circuit containing the gauge and sensor.

How Does an Oil Pressure Gauge Work

Types of Oil Pressure Gauges

There are two types of gauges: electric and mechanical.

Electric Oil Pressure Gauges

Most modern cars have electric oil pressure gauges. The power for electric gauges is supplied from one of the many wires stashed behind your vehicle’s dashboard. A current flow through a coil and measures resistance in the instrument’s return wire.

This resistance corresponds to oil pressure. Electric gauges are typically easier to integrate into modern circuits, which is one reason they’re installed in the majority of newer cars.

Mechanical Oil Pressure Gauges

Mechanical gauges use pipes instead of wires. This creates what some technicians consider to be a more trustworthy reading, but it also poses an increased risk. Instead of measuring resistance with electrical currents, mechanical gauges funnel oil into small pipes at the same pressure it flows in the engine.

If anything punctures the oil pipe, it could start spewing oil at engine pressure! Because of this, mechanical gauges can require more attention and maintenance than electric gauges.

Pros and cons

Electric gauges are easier to integrate into the modern one-piece printed circuit instrument panels used in most modern cars, they are less bulky and it’s easier to route and connect a wire than a pipe.

Mechanical gauges are not as common as electric ones, although they are still available in accessory shops. Because the oil arriving at the back of the gauge is at engine pressure, you have the problem of messy leaks if the pipe comes undone. However, some people find a mechanical gauge more trustworthy.

How To Read an Oil Gauge?

Oil gauges look like most indicators on your dashboard. There’s a label (typically “OIL”), numbers (ranging between 1-80 or 1-100), and a dial with an indicator needle. Instead of numbers, some vehicles use “L” and “H” to indicate high or low pressure. For a baseline reading, check your owner’s manual for the manufacturer’s recommendation.

Psst! While almost every vehicle has a system for monitoring oil pressure, not all vehicles have oil pressure gauges on the dashboard. It depends on the make and model. Some vehicles provide a digital reading and others have a dashboard light that flicks on when a change in oil pressure is detected. Refer to your owner’s manual for the final word on where your oil pressure gauge is located and how to read it.

Troubleshooting Oil Pressure Gauge Issues

There are some oil pressure gauge readings that you shouldn’t ignore. Here are three common readings that indicate a problem with the oil pressure or a larger engine problem.

Zero Reading

This is normal only when the vehicle is idling. If this reading occurs at higher speeds, it could mean one of three things: 1) the gauge is faulty, 2) the oil level is low, or 3) the oil pump (or its drive) is broken. In any case, switch the engine off and get your engine checked out as soon as possible.

Low Reading

If your oil pressure gauge consistently reads a lower number while the vehicle is idling (typically below 20 or in the lower quarter of the gauge) get it checked out. It could indicate an issue with the gauge (like a leak in a mechanical gauge), but it most likely means an engine component has worn down, creating a drop in oil pressure. By fixing or replacing the part quickly, you could avoid major—and expensive—engine damage down the line.

High Reading

The needle on the pressure gauge should settle at the midpoint after the car has been running for about 20 minutes. If it settles toward the top of the gauge, it could be indicating high oil pressure. The pressure relief valve could be stuck or faulty, or there could be a blockage in the oil delivery lines. Since high pressure could cause your oil filter to burst, switch off your engine as soon as you notice the reading.

Your car’s gauges, indicators, and lights were made to help you! They clue you into issues that may not be readily apparent before they end up costing you significant time and money. If your oil warning light is on or you get a reading on your oil pressure gauge that concerns you, let our professional technicians ease your mind with a full-service oil change. This service includes a 19-point inspection that can help diagnose your car’s oil pressure issues.