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 measures the oil pressure in your engine. It’s typically found on the dashboard of your car. Your oil pressure gauge informs you of how much oil remains in your vehicle, but it’s also an indicator of your engine’s general health.
If you notice your car has low oil pressure, we recommend having a qualified technician inspect it. Low oil pressure can be indicative of various problems, including:
- An oil pump failure
- A broken hose
- A leaking gasket
How Does an Oil Pressure Gauge Work?
The oil pressure gauge works as a monitor, and its job is to see the oil pressure in the main oilways near the filter and the pump. The engine block has a tapping and either an oil pipe or a sensor screwed into it.
The oil warning light has a sensor and is screwed into the T-piece or the union. It doesn’t matter if the car has a fitted oil pressure gauge or not.
The mechanical gauges work because the engine’s pressure forces the needle into the dial. On the other hand, electrical gauges work with a sensor that produces variable resistance and is screwed into the engine block. This affects the circuit that has the sensor and the gauge through the current that passes through it.
Types of Oil Pressure Gauges
There are two types of gauges: electric and mechanical.
Electric Oil Pressure Gauges
A fused power supply provides electric current to the gauge, and the current is supplied from printed tracks or one of the wires behind the dashboard. A wire-wound coil that is mounted within or around the needle’s pivot passes the current and produces a magnetic field.
This field is responsible for moving the needle across the gauge. The amount of current decides which reading to give and how far the scale goes. It depends on the gauge’s return wire’s resistance, which you will find is earthed to the engine block with the help of a sensor.
Oil pressure decides the sensor’s resistance, and oil enters the sensor’s end by pushing against a diaphragm screwed into the engine block.
Mechanical Oil Pressure Gauges
Mechanical oil gauges don’t use wires but instead use pipes. Technicians believe that this not only creates a trustworthy reading compared to wires but also creates risks.
Instead of using electrical currents to measure resistance, the mechanical gauge funnels oil into the small pipe simultaneously at the same pressure at which it flows in the engine.
The oil pipe is placed in such a way that it is away from anything that could damage it, as it could lead to the spilling of oil if the pipe is damaged. Mechanical gauges require more attention and delicacy than electric gauges.
The Difference
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.
Faulty Oil Gauge Symptoms
Most oil pressure gauges are not wear and tear items except on mid-2000s Chevy pickups, where the tiny servo that drives the gauge needle may fail, which is common with any or all of the gauges on those platforms.
Here are the most common indicators of a problem with the oil pressure gauge:
Oil Gauge Low
If the gauge is reading low, it’s best to err on the side of caution, check the oil, and have the engine oil pressure checked by a shop with a mechanical gauge.
As engine parts wear and oil pressure is lost through worn bearings (the oil gets thinner when it’s hot), the oil pressure might look acceptable when the engine is first started cold only to drop as the engine oil heats up. A good rule of thumb for acceptable minimum oil pressure is 10 psi per 1000 rpm. The optimum oil pressure would be from 40 to 60 psi with a hot engine.
Oil Gauge High
Does the oil pressure gauge show low-pressure readings while the engine idles? If the readings drop below 20 psi or stay in the gauge’s lower quarter, you might have a faulty oil gauge, but more importantly, you might have low engine oil pressure, which you should always have checked as soon as possible.
Pro Tip: Since many engines use oil pressure for their timing chain tensioners, low engine oil pressure may cause the timing chains to rattle. If you hear noise like this on a Dodge or a Ford, have the engine oil pressure checked by a shop.
A mechanical oil pressure gauge can develop a leak. Oil leaks reduce oil pressure, leading to the part showing inaccurately low readings.
For electric oil pressure gauges, issues with their wiring and other problematic components can affect the accuracy of their readings.
Oil Gauge Is Zero
If the oil gauge indicator needle stays at zero even though you can hear and feel the engine running without unusual noises, the sending unit can be checked by shorting the oil sender wire to ground (be careful not to damage the terminal) and watching the gauge to see if it responds to that ground. If it does, the sending unit might need replacing.
Usually, the oil pressure gauge will only show zero psi when the engine is turned off or idling unless there’s a problem with the sending unit, the gauge, the wiring or one of the modules that reports the oil pressure. When you start driving at higher speeds, the oil pump sends more lubricant through the system, which registers an increase in psi. If the needle doesn’t move from zero, the gauge might have stopped working.
Other reasons for the oil pressure gauge showing zero psi include a faulty oil pump or a low engine oil level.
How Do I Read My Chevy’s Oil Pressure Gauge?
Check your vehicle’s dashboard to locate your oil pressure gauge.
Your oil pressure gauge will typically have a distinct label, such as “oil.” Some oil pressure gauges display numbers ranging from 1 – 80 or 1 – 100 via a digital display or an indicator needle. However, your car may keep things simple with an “H” to indicate high oil pressure or an “L” for low oil pressure.
To get the most accurate results, we recommend establishing a baseline reading on your oil pressure gauge after you’ve had a tune-up and oil change. This number can be considered your vehicle’s healthy standard.