Low Oil Pressure At Idle: Quick Diagnosis, and Easy Fix!

If your car is idle or stopped while the engine is running and you notice that the oil pressure gauge is not reading high, it means that your vehicle is facing low oil pressure issue at idle.

In this post, we’ll show you how to diagnose and fix the low oil pressure issue of your car while it is idle.

So, what causes a car’s low oil pressure at idle? Low oil pressure at idle can occur due to various factors. These can include a faulty oil gauge switch, blocked oil filter, or dirty oil pressure sensor. Additionally, leaks in the oil line, old or conventional engine oil, and a damaged oil pump can influence oil pressure. Finally, worn-out engine parts may also result in low oil pressure at idle. Ensuring proper maintenance and cleaning can counter these issues.

What is Oil Pressure In a Vehicle?

oil pressure reading on vehicle dashboard

Oil pressure is the amount of oil being delivered by an oil pump to the different parts of a vehicle. Oil pressure is measured in pounds per square inch (PSI). The oil pressure gauge in your car is used to check the oil pressure in your car’s engine.

The pressure of the oil delivered to the engine depends on the oil pressure of the engine, the amount of oil in the tank, the number of engine revolutions per minute (rpm), and the size of the engine.

A low oil pressure may indicate that the oil filter is clogged, or that the oil is dirty. It could also indicate a malfunction in the engine itself.

How Does Oil Pressure Work in Engine?

The oil pressure is generated by the engine through the movement of pistons within the cylinder. 

The oil pressure is the force pushing the engine oil through the oil pump to engine oil channels, pipes, and filters. Oil pressure is determined by the thickness of oil and its resistance level as the oil flows through the engine’s channels.

Check out the video below to understand the importance of oil circulation in an engine.

When the oil pressure is low, the engine will run rough. The oil pressure is a pressure exerted by the oil that lubricates the engine. This pressure prevents friction between moving parts. If the oil pressure is low, the engine will run rough.

The reason for increasing oil pressure when a car accelerates is that the oil pump would also need to spin faster so that the engine would have enough oil to lubricate the components of the engine as they move faster and start generating more heat.

So, as more power is supplied to the engine via acceleration, more pressure of oil is built up as indicated by the oil gauge.

Just like the oil pressure in the engine increases with speed, there has to be a certain oil pressure when the vehicle is idle. So, when the car is stopped or the engine is running at idle, the minimum oil pressure should be between 15 and 70 psi.

At this point, I would like to highlight is that the idle oil pressure is a function of the type of engine, engine condition, the grade of oil you are using, the engine operating temperature, and the engine idle speed.

The cold idle oil pressure of an engine in a normal condition is from 40 to 65 psi, and the hot idle oil pressure of an engine in a normal condition is from 10 to 30 psi.

As the vehicle travels several miles, the clearances between engine parts increase due to wear and tear. As a result, oil pressure decreases as the vehicle mileage increases.

If the oil pressure is low, the oil pressure senders will trigger a warning light on the dashboard.

If the engine is running and the oil pressure drops below the minimum oil pressure, the engine will stall. This could be caused by low oil pressure due to poor maintenance or a leak.

Symptoms of Low Oil Pressure At Idle

Here are the symptoms of low oil pressure at idle:

  • Engine overheating
  • Illumination of low oil pressure warning light on the dashboard
  • Illumination of the check engine light
  • Misfire and Rough idling of the engine on cold startup
  • Knocking and ticking sound

1. Illumination of Low Oil Pressure Warning Light on the Dashboard

The first symptom of low oil pressure at idle is a low oil pressure warning light on the dashboard. If the oil pressure sensor senses that the oil pressure is too low, it will activate the low oil pressure warning light.

2. Engine Overheating

Since motor oil also absorbs heat from the engine. If the oil pressure is low at idle, it will cause the engine to overheat. The low oil pressure at idle also causes excessive friction between engine parts (crankshaft, camshaft, main and rod bearings) that causes them to overheat.

3. Misfire and Rough Idling of the Engine On Cold Startup

A misfire occurs when the engine fails to fire a spark plug. An engine misfire can cause the rough idling of the engine. Basically, there is a component in the engine called a “cam phaser” that operates through the oil pressure.

When the oil pressure is low, the cam phaser will go bad, which will affect the valve timings of the engine. As a result, inefficient combustion will take place, due to which there will be rough engine idling on cold startup. You can also check my guide on cam phasers to know how they operate, and how they can cause engine idling.

3. Knocking and Ticking Sound

A whining, knocking, and ticking sound in the engine can also indicate low oil pressure at idle. This is mainly caused due to low oil pressure in the main bearing and rod bearing.

The main bearing is present between the crankshaft and engine block. The main bearing is responsible for supporting the crankshaft. Rod bearing is present between connecting rod and crankshaft. When there is low oil pressure at idle, less oil will be present in main and rod bearings, due to which a knocking sound will be produced in the engine.

From the picture below, you can understand the main and rod bearings in a better way.

5. Illumination of the Check Engine Light

Like low oil pressure light, there is also a check engine light on the dashboard that shows that something is a problem with the engine. Check engine light usually illuminates when there is misfiring in the engine, which can be caused by low oil pressure as discussed above.

causes of low oil pressure at idle

Here are the causes of low oil pressure at idle:

  • Low oil level
  • Bad quality of oil
  • Clogged oil filter
  • Faulty oil pressure sensor
  • Faulty oil pump
  • Worn-out parts of the engine

1. Low Oil Level

Low oil level in the oil pan can be the cause of low oil pressure at idle. You can measure the oil level from the dipstick mark.

measuring oil level using dipstick

When the oil level drops below the lowest dipstick mark, the engine’s oil pump is unable to keep up with the demands of the engine. The dipstick has usually two marks that stand for “low” and “full”.

The oil level should be between those marks. In some cars, a dipstick has a cross-section instead of marks; in this case, the level should be within the cross-section.

The engine runs at reduced oil pressure until the oil level rises below the lowest dipstick mark. If you’re in doubt, you can check the owner’s manual of your vehicle to get an idea of how to read the dipstick mark.

Another way of diagnosing a low oil level in the engine is the noise in the crankcase. Oil in the crankcase is responsible for lubricating the crankshaft. If there is a knocking or rumbling sound in the engine, the chances are that the oil level is lower.

Here is how to fix low oil level in an oil pan:

  • Add engine oil to the correct level.  
  • Check if there is a leak in the oil pan.
  • Check the gallery gaskets as the leaking oil can also cause a low oil level. Replacing gallery gaskets is a pretty expensive and invasive job.
  • Check oil pan gaskets.
  • Locate oil rear and front seals with the help of a manual, and check if they are worn out. I would recommend you to first check the rear main seal that keeps oil sealed inside the rear of the engine, where the crankshaft connects with the transmission. I found this guide helpful for replacing oil seals.

I found this great video that is demonstrating when a gallery gasket needs to be replaced.

2. Bad Quality of Oil

dirty engine oil

Bad oil quality can also cause low oil pressure at idle. With time, motor oil becomes thinner because of engine heat, due to which it cannot maintain the desired oil pressure. As a result, the oil starts to lose its temperature-viscosity properties.

Also, oil becomes dirty when it flows through different parts of the engine. Not changing the oil cause sludge buildup, which will block the oil passageways.

This impacts the ability of the oil to protect the engine from wear and corrosion, and its ability to clean the engine.

Due to this, engine oil properties are also affected which can cause low oil pressure at idle. Check out this guide in which it has been explained how dirty oil looks when you check it through a dipstick.

Ultimately, when the oil is bad, the engine can become damaged due to high friction between the engine parts.

It is necessary to change the oil after every 5k to 10k miles so that the optimum oil pressure can be maintained in the engine at idle.

3. Inappropriate Oil Viscosity

If the oil viscosity is too low or too high, it can cause low oil pressure at idle. I would highly recommend you first check out my guide on the importance of the viscosity of oil in vehicles. In this guide, I have explained when to use 5w30 oil instead of 5w20.

Each engine is designed to use a motor oil of a certain type and viscosity grade based on the tolerances of engine parts, such as bearings.

Oil viscosity shows how easily motor oil can flow around the engine at any specific temperature.

If you use motor oil during extreme cold temperatures, it can be beneficial in the cold-start lubrication. But in summers, the motor oil will flow too thin that it will cause low oil pressure at idle.

That’s why engineers have introduced multi-grade motor oils that are formulated for both hot and cold temperatures.

Old vehicles with high mileage use high viscosity oil, such as 10w30 or 5w30 as the clearances between the engine parts tends to increase as the engine travels several miles.

I would highly recommend you to consult your vehicle’s manual to find the correct viscosity grade of oil. Moreover, in the owner’s manual, the type of motor oil has also been mentioned.

If the manufacturer recommends using synthetic oil, you should not use conventional motor oil as synthetic motor oil is more stable at extreme high and low temperatures.

4. Clogged Oil Filter

clogged oil filter
Source: https://www.quora.com/Can-a-clogged-Oil-filter-cause-a-car-to-lose-power

Clogged oil filter is a common reason for low engine oil pressure. The oil first passes through oil filter before it flows through engine oil galleries.

Oil filter in the engine is used to clean the debris and dirt out of the motor oil. If the oil filter becomes clogged with debris, it will deprive the engine of its necessary oil supply. As a result, there will be low oil pressure at idle, the engine will run dry and it won’t function properly.

When changing oil filter, keep in mind that it should be in accordance with the OEM specifications. Don’t buy cheap FRAM Oil Filters. Always consult your vehicle’s manual for the most suitable oil filter for your vehicle.

Check out the video below to know about the symptoms of a bad oil filter.

5. Faulty Oil Pressure Sensor

oil pressure sensor in engine

The oil pressure sensor is a device that senses actual oil pressure in an engine and sends electric signals to the engine control unit.

The oil pressure sensor works by sensing the pressure through the spring and diaphragm mechanism. The location of an oil pressure sensor depends on the make, model, and engine.

The engine control unit perceives the electric signals from the pressure sensor and transfers the information to the vehicle’s oil pressure gauge and warning light. When the oil pressure drops below the preset level, it sends a signal to the ECU which then issues a warning light on the dashboard.

Now, there are chances that the oil pressure is fine at idle, but the faulty oil pressure sensor is sending wrong signals to the engine control module, due to which wrong oil pressure is displayed on the gauge and the oil pressure light turns on the dashboard.

There are two possibilities that the oil pressure sensor is faulty:

  • Spring has worn out
  • Oil is leaking out of the pressure sensor
  • The electrical part is all covered with oil

To verify if it is the faulty oil pressure sending unit that is showing low-pressure signals to the pressure gauge, you can perform an oil pressure test by following these steps:

  1. Turn off the ignition switch.
  2. Set the hand brake.
  3. Open the bonnet of your vehicle.
  4. Locate the oil pressure sensor. You can take help from the owner’s manual.
  5. Remove the oil pressure sensor with a wrench.
  6. Screw the oil pressure test kit into the port for the engine’s oil pressure sending unit. You can get an oil pressure test kit from here.
  7. Start the engine and shift it to the neutral position.
  8. Wait for a few minutes to warm up the engine.
  9. Check the PSI reading at idle.
  10. If the oil pressure on the oil test kit lies within the range of normal oil pressure at idle, it means that the oil pressure sending unit is faulty.

I found the below video helpful to understand the oil pressure sending unit.

6. Damaged Oil Pump

The oil pump is a small, circular device that turns within a chamber of the oil pan. The oil pump in your engine is responsible for moving the oil through the engine.

The oil pump fails when the internal gear mechanism of a pump wears down, which affects its pumping capacity due to an increased clearance between the oil pump gear and casing.

If the oil pump malfunctions, the engine will run with low oil pressure at idle, causing a loss of power.

oil pump internal gear

7. Worn-out Parts of the Engine

As the car mileage increases, the clearances between the engine parts also increases due to wear and tear.

Since the oil pressure is determined by the resistance oil faces to flow through engine oil galleries and critical components like bearings, the increase in clearance between engine parts will cause decrease in the oil pressure.

Bearing is an important component you need to first replace as it has a large impact on the oil pressure.

Take your car to the dealership. Measure main and rod-bearing clearances. If they are worn beyond the critical bearing clearance specified in the owner’s manual of the vehicle, the bearing needs to be replaced.

Another fix for low oil pressure at idle you can do when the engine parts have worn out is to use a higher viscosity grade oil. If the manufacturer recommends 5w20 oil, you can use 5w30 oil in such cases.

Can Synthetic Oil Cause Low Oil Pressure?

Synthetic oil causes slightly low pressure at idle. But, this shouldn’t be a problem. Synthetic oil has better flow characteristics than conventional motor oils due to its uniform molecular structure. Keep in mind that it is the oil flow that lubricates the engine, not the oil pressure.

Synthetic oils face less resistance to flow due to their better flow characteristic. As a result, synthetic oil generally flows easier than the same weight conventional and thus runs at a lower pressure.

Due to this reason, the oil pump does not have to work harder to flow the oil. So, you will observe a slightly lower pressure with synthetic oil. The film strength on a good synthetic is pretty good which means synthetic oil doesn’t need a lot of pressure to protect against friction.

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