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What Causes Low Engine Oil Pressure?

Dan Ferrell writes about DIY car maintenance and repair. He has certifications in Automation and Control Technology and Technical Writing.

There are several causes for low oil pressure.

There are several causes for low oil pressure.

Low Oil Pressure in Your Car

Here are the four most common reasons for low oil pressure in a car:

  1. Low oil level
  2. Worn-out oil
  3. Overheating
  4. Worn-out bearings

Oil may be the lifeblood of your engine. But without good oil pressure, your engine is in serious trouble.

Although low oil level is the most common reason for low oil pressure, there are other preventable conditions that cause it, which car owners may neglect. For example, with the new extended periods for oil changes in modern engines, car owners do not only forget to check oil level between changes, but they also forget to change the oil when it loses its efficiency.

And if you drive mainly in stop-and-go traffic, the oil usually needs changing before the recommended change interval. Most manufacturers' suggested oil change intervals apply to ideal driving conditions: driving at highway speeds for at least 20 minutes every day. But most vehicles are driven within the city, on short trips with frequent stops. Short trips don't allow engine oil to reach its operating temperature and reduce its service life.

Of course, there are other things that can cause not only low oil pressure but high pressure as well.

What's in This Guide

This guide will explain:

  • what the oil pressure should be;
  • what low pressure means for your engine;
  • how normal oil pressure can be upset;
  • and some symptoms caused by low oil pressure.

Towards the end, you'll find some troubleshooting procedures that can help you determine whether your lubrication system is working outside its proper oil pressure parameters.

But first, let's take a look at normal oil pressure.


1. What Should My Oil Pressure Be?

2. So What Does Low Oil Pressure Mean?

3. Low Oil Pressure Causes

4. Low Oil Pressure Symptoms

5. My Low Oil Pressure Warning Light Comes On and off

6. I Have Low Oil Pressure at Idle

7. My System Has High Oil Pressure

8. Will Low Oil Pressure Cause a Vehicle Not to Start?

9. How to Check Oil Pressure

10. Further Diagnostic Tests

Low oil level will drop oil system pressure.

Low oil level will drop oil system pressure.

1. What Should My Oil Pressure Be?

Normal oil pressure may vary slightly from one vehicle model to another.

When there's proper pressure, you'll see the needle on the oil pressure gauge at about the middle of the scale, and you won't see the low-pressure warning indicator light come on.

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When your engine is at operating temperature, a typical system pressure may fall within a range of 20 to 30 psi at idle (140 to 200 kPa), and 45 to 70 psi (310 to 482 kPa) at driving speed.

For the exact specifications, check the vehicle repair manual for your particular make and model. If you don't have the manual, you can get an inexpensive, aftermarket copy from Amazon. Haynes manuals (get the one for your exact model and year) come with step-by-step procedures for many maintenance, repair, and troubleshooting tasks. So the manual pays for itself after your first maintenance project.

System pressure allows oil to travel throughout the lubrication system.

System pressure allows oil to travel throughout the lubrication system.

2. So What Does Low Oil Pressure Mean?

To properly lubricate, cool, and clean critical components like crankshaft and camshaft bearings, pistons, and other moving parts, there should be adequate oil flow and pressure in the lubrication system. Together, flow and pressure allow lubrication of components under the valve cover at the top of the engine as well.

To do this, the oil pump has to push oil through narrow clearances under bearings and galleries. It is these narrow passages that build pressure in the system because they restrict the rate of oil flow. The faster the engine moves, the higher the rate of oil flow and the higher the pressure.

Too much pressure can be damaging to engine components, though. A relief valve close to the oil pump opens when the pressure reaches a predetermined value, usually between 45 and 75 psi, allowing extra oil to drain back into the oil pan.

However, when the lubrication system can't maintain proper oil flow, or pressure drops when it should not, engine components are going to be starved of much-needed oil.

Using oil with the wrong viscosity for the application will upset system pressure.

Using oil with the wrong viscosity for the application will upset system pressure.

3. Causes of Low Oil Pressure

One or more factors can contribute to a drop in oil flow or system pressure, for example:

  • Not enough oil in the system. This is perhaps the most common cause of low oil pressure. With wider intervals between oil changes in modern vehicles, car owners forget to check oil level between changes.
  • Aged oil that has lost its viscosity. This happens when car owners forget to change engine oil at the manufacturer recommended intervals or as necessary. This is another frequent cause of low oil pressure.
  • Using oil with a much lower viscosity than that recommended by the car manufacturer.
  • Engine overheating will cause oil to thinner, preventing proper pressure to buildup. This is similar to using oil with a much lower viscosity than recommended.
  • Too much clearance between the engine bearings and journals due to wear. This is common in high-mileage engines.
  • A worn-out oil pump with wider clearances between the rotors can cause a drop in the rate of flow, although this is not as common.
  • Worn-out piston rings, cylinder walls, valve stem seals, or guides will allow oil to enter the combustion chamber and get burned, causing a drop in engine oil level and pressure. Usually, you'll notice some blue smoke coming through the tailpipe when this happens. Fuel can also dilute engine oil this way, causing a drop in pressure.
Valve clattering sounds can be a sign of low engine pressure.

Valve clattering sounds can be a sign of low engine pressure.

4. Symptoms of Low Oil Pressure

A few indicators can point to problems with oil system pressure:

  • Knocking or clattering sounds coming from the engine during operation. This is perhaps the most common symptom.
  • Oil pressure gauge reading lower than usual at idle.
  • Poor starting.
  • Loss of engine performance.
Modern vehicles come equipped with a low oil pressure warning light.

Modern vehicles come equipped with a low oil pressure warning light.

5. My Low Oil Pressure Warning Light Comes On and Off

Most modern vehicle models come with an oil pressure switch that activates a warning light on the dashboard when dangerously low oil pressure is detected.

For the light to come on, oil pressure has to drop below 5 or 10 psi at idle, depending on vehicle model.

Unless pressure drops suddenly, you may first become aware of knocking or clattering sounds coming from the engine. This may happen, for example, when not enough oil gets to the valve train or engine bearings.

However, a flickering warning light may also happen when a fault appears in the oil pressure switch or its electrical circuit.

The next procedure can help you check the operation of the indicator light or oil pressure gauge, if necessary.

Most sending units or switches are located next to the oil filter. If you need help to find the unit, consult your vehicle repair manual.

To check the operation of the warning light or oil pressure gauge:

  1. First, make a visual inspection of the electrical wire connected to the oil pressure sending unit or switch. Check for signs of damage.
  2. Check the connection. It should be tight and clean.
  3. Then, disconnect the wire from the sending unit

    • If the warning light remains on, the circuit is grounded, and you need to find the fault.
    • Similarly, if you have a gauge, when disconnecting the sending unit, if the gauge reading remains indicating low pressure, the circuit is grounded, or there's a mechanical problem with the gauge.
  4. After disconnecting the wire, ground the warning light or gauge by touching a metal component or an unpainted surface on the engine with the wire.

    Now, either the indicator light should come on, or the oil pressure gauge should read minimum pressure

    Otherwise, there’s something wrong with the indicator light or gauge.

    Some pressure sending units can be tested with a digital multimeter by checking their resistance. Consult your vehicle repair manual.

NOTE: On modern vehicle models, some manufacturers recommend using a special gauge tester to check for proper indicator operation. This is usually done on vehicles where the oil pressure system is controlled by the car computer. Consult your vehicle repair manual.

Whether or not your tests show the warning indicator light or gauge is working properly, it is a good idea to check system pressure. Head over to the section How to Check Oil Pressure below for the procedure.

Low oil pressure is more likely to appear during engine idle.

Low oil pressure is more likely to appear during engine idle.

6. I Have Low Oil Pressure at Idle

When the oil warning indicator light or the oil pressure gauge reads too low at idle, it can mean one of several things:

  • Low engine oil level
  • Engine oil is worn
  • Overheating is causing the oil to thin
  • Oil pump not working properly
Adding too much oil will upset lubrication system pressure.

Adding too much oil will upset lubrication system pressure.

7. My System Has High Oil Pressure

Although low oil pressure is the most common problem when there's something wrong with the lubrication system, high oil pressure can also happen.

High oil system pressure shows up when system pressure goes beyond the upper limit parameters in the system.

High system pressure may be caused by the following conditions:

  • Pressure relief valve sticking closed. This valve is located in the engine oil pump or close to it. The valve limits the maximum oil pressure allowed in the system and opens when the maximum allowed pressure is reached, usually between 40 and 60 psi, depending on the model. Otherwise, the pressure will rise. Debris or sludge or thick oil may clog the valve.
  • High-viscosity oil. Using a 20W-50 oil in a modern, low-mileage passenger vehicle, for example, can cause high oil pressure. Something similar may occur if the thermostat sticks open. The engine won't reach operating temperature, and the oil won't thin enough to properly do its job.
  • Restricted oil galleries or passages. Debris or sludge can clog passages and prevent engine oil from reaching crankshaft bearings and other system components.
  • Adding too much engine oil. Check oil level by reading the dipstick, and consult your car owner's manual or vehicle repair manual for engine oil capacity for your particular vehicle model.
  • Plugged oil filter or engine block bypass valve. This usually occurs when debris or buildup accumulate inside the bypass valve to prevent oil flow. Also, this can happen if you haven't replaced the oil filter during the last few engine oil changes.
Low oil pressure can prevent the engine from starting on some vehicles.

Low oil pressure can prevent the engine from starting on some vehicles.

8. Will Low Oil Pressure Cause a Vehicle Not to Start?

Some vehicle models come equipped with a low-oil-pressure safety circuit.

The circuit connects to the car computer, and the computer disables the ignition system when too much oil pressure is lost.

This is to prevent the engine from serious mechanical damage.

Check your vehicle repair manual, if necessary, to see if your model has this switch installed, and, if necessary, check oil system pressure using the following procedure.

The oil pressure switch or sending unit is usually located next to the oil filter.

The oil pressure switch or sending unit is usually located next to the oil filter.

9. How to Check Oil Pressure

You can use an oil pressure gauge tester to check the lubrication system in your vehicle.

Proper lubrication system pressure depends on:

  • Good operation of the oil pump
  • Certain system components being within specifications
  • Adequate clearance between bearings and journals
  • Clean galleries

The gauge can give you information about the condition of the oil pump, and the lubrication system in general.

If you don't have an oil pressure gauge, you may borrow one from your local auto parts store.

  1. First, locate the oil sending unit or switch. This is usually mounted next to the oil filter. If necessary, consult your vehicle repair manual.
  2. Unplug the sending unit's electrical connector. Then, remove the sending unit using a wrench.
  3. Connect the correct fitting to the gauge's hose to plug the gauge in place of the sending unit. You may also connect the test gauge in one of the oil cooler lines, if your engine uses one (usually found in diesel, turbocharged, or high-performance vehicles). If necessary, consult your vehicle repair manual.
  4. Start the engine and let it idle for 15 or 20 minutes so that it reaches operating temperature.
  5. Increase engine speed to about 1,000 rpm and check engine oil pressure.
  6. Increase engine speed to about 2,500 rpm and note engine oil pressure.
  7. Compare your readings to the specifications listed on your vehicle repair manual.

    • If oil system pressure is lower than specifications, you need to find out the cause.
    • If the pressure is within specs, and the engine operates without knocking or rattling noises, engine oil has the correct level and is in good condition, and there are no overheating issues, then there may be a problem with the engine oil pressure sensor, oil pressure gauge or indicator light. Or the electrical circuit.

NOTE: Specific test procedures may differ from the one indicated here. Consult your repair manual, if necessary.

A worn oil pump can also cause low oil pressure.

A worn oil pump can also cause low oil pressure.

10. Further Diagnostic Tests

Some common problems related to low engine oil pressure, and high oil pressure, are discussed here. As you can expect, knowing the exact cause of the problem will help you make better repair decisions and prevent further, unnecessary repair expenses.

Although it's not as common as the above causes, don't forget that a failed oil pump can also upset system pressure. A failed pump may leak internally; its relief valve may clog or become weak; the screen may clog, or its driver may fail. If necessary, you can install a new or rebuilt unit.

If the oil pump in your vehicle fails, make sure the problem is only with the pump itself. A worn out pump is rare and may suggest, especially on high-mileage engines, worn-out engine bearings as well.

Sometimes, more than one test, including a prelubricator test, may be necessary to pinpoint the cause behind a problem with the lubrication system.

Some car owners seem to have found a practical way to deal with clogged oil pump screens. Watch the video below for some tips about cleaning this device without removing the oil pan. These tips may work for you too.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Questions & Answers

Question: I have a 2008 Cadillac Escalade. It shows low oil pressure and I stop the engine. When I start the car, also I can see the coolant leaked on the ground and the temperature gauge is at zero. When the needle comes to the middle of the temperature gauge, the car will run smoothly no oil pressure warning nothing. Why is it so?

Answer: There could be a loose or corroded connection. Once temperature builds up, current in the circuit overcomes the resistance. This is just a guess. Circuits with too much resistance sometimes behave this way. You should take care of the coolant leak first and then diagnose the low oil pressure issue. Both of these problems can cause extensive damage.

Question: I have a 2011 GMC Sierra 1500. It keeps warning of low oil pressure. My husband has changed out the sensor twice, and it keeps saying low oil pressure stop engine. How do I fix it and what else could be wrong?

Answer: First, make sure that the engine is actually losing oil pressure. Check the oil level, and oil condition. Also, make sure you’ve changed the oil filter according to schedule (you’ll find the maintenance schedule in your car owner’s manual or vehicle repair manual). You can hook a pressure gauge and check the actual pressure. Usually, the problem is with the sending unit or the wiring, or dirt interfering with the sender operation. If oil pressure is actually low, go over the post to see possible causes.

Question: I have a 2009 model, with a 1.2 L engine that shows an oil low indication in idle. If I increase the rpm slightly, the indicator turns off. Why is this?

Answer: Check section “VI. I Have Low Oil Pressure at Idle” in the post to get an idea about the problem.

Question: I have 2008 Dodge Durango 5.7 Hemi. The oil pressure light blinks on and off. I've cleaned the sludge out, and there's no knocking. It is still doing the same thing. I replaced the oil pressure sensor three times. Do you have any suggestions?

Answer: Make sure you've changed the oil filter as well. When installing the sensor unit, wrap some RTV around the threads as well. Check the oil pressure to make sure you actually have low pressure. There could be a problem with the sender unit circuit or an actual pressure problem. If so, check the post for some clues.

Question: I have a BMW 320td 2008 model. All of a sudden this low oil pressure sign appeared. I stopped at a garage for 30 minutes. I started the car and went home. The sign was gone till I reached home. Any reason why?

Answer: Usually, this is because of low oil level, oil that has very low or no viscosity (worn oil), overheating (having the same effect to some extent as the previous point). Another common reason is a faulty pressure switch. However, if you've put too many miles, bearings may be worn and causing a drop in pressure.

Question: I have a 2000 Chevy Silverado and the oil pressure is running low, 20-40, psi and the gauge ticks like a clock. Is this a sign of the oil pump failing?

Answer: Check the oil pressure sending unit first. If it’s working fine, do an oil pressure test.

Question: How low does the oil level in a 2018 Dodge Ram 2500 have to be before the low oil pressure light comes on?

Answer: I don’t have the specific specs for your model, but usually, the low oil pressure light will come on at approximately 1Qt or 2Qts low, depending on the model (possibly 3 on your model). But be aware that this is for low oil pressure, so there are other reasons that will trigger the warning light.

Question: I have a Chevy Impala 2001. When going uphill, it jerks and slows down. What could possibly be the cause?

Answer: It seems like a misfire. Have you changed the spark plugs and plug wires? Start there if service schedule is due for the ignition system.

Question: I have a 2004 Ford Explorer Sport Trac. When I start the engine everything is normal, but when I start driving and the engine heats up, the oil pressure drops suddenly, and the engine starts to sound. Any reason why?

Answer: This is usually caused by a worn oil pump or a problem with the pump's pressure relief valve sticking open. Your engine oil filter should have an oil pressure relief valve. If you haven't changed the oil filter since the low oil pressure issue starter, replaced the oil filter and see if this fixes the problem. Another common reason for the drop in oil pressure is worn out bearings on high mileage engines. If necessary, have the problem properly diagnosed before deciding on any repairs.

Question: I have a 2015 Dodge journey v6 with 80k miles, and my oil pressure is reading 80 and then drops to 30-40 PSI. There is a knocking noise coming from the manifold, but there is no visible damage. Can you help?

Answer: Make sure you’ve replaced the oil filter according to your manufacturer schedule. A clogging passage can raise oil pressure and starve components from oil. This may explain why you are hearing the knocking noise.

Question: I have a 2003 Ford Focus SVT. It has a 2.0L Zetec engine. My oil pressure gauge is showing just a tiny bit low at 3,000 rpms. I have no light coming on but my performance is lacking. No knocking or noise and my oil level is good and the oil is still good. Any hints on what my problem could be?

Answer: Check the specs for your particular model and that you are using the correct oil for your application. Once warmed, you should get about 10psi 20psi or more at idle, and around 30psi or more at 3000 rpm. The loose in psi may be a sign of pump or engine wear, but losing a bit of pressure shouldn't be of concerned. If necessary, you can double-check with an oil pressure gauge and compare. Sometimes, if the oil pump is damaged, the computer will go into limp mode and you'll see a lack of performance, but your pump may be working okay. You may want to double-check for pending trouble codes, even if the engine light is not coming on, just in case.

This other post may help as well:

Question: I have a 2009 Toyota Corolla with 130K miles on it. After an engine flush, a strange, loud tapping noise started. What do you think it is?

Answer: Usually, this type of noise develops when hydraulic lifters don’t get the proper oil pressure to maintain the correct clearance. I don’t know if your particular model uses this type of lifters. But valvetrain mechanical issues can also cause. Make sure you are using the oil and filter recommended by the manufacturer. If necessary, check the oil pressure.

Question: Engine oil pressure low alarm at 600 rpm and at 85° temprrature. What should we do?

Answer: Test the oil pressure, make sure it is low. Then start troubleshooting.

Question: What should I do if my oil warning light keeps on flashing and making noise?

Answer: The problem could be with the oil sensor or actual low fuel pressure. Check pressure first to make sure it is to specs. Compare your number with the one in your repair manual. Then, if necessary, check the sensor.

Question: I have a Dodge Journey 2015, with the engine’s rpm going low, maximum 4000 rpm. At the same time, the oil warning light blinks. I scan the computer and it says there’s something wrong with the oil pressure controller. I don’t know what it is? Is it Oil pump? Or feed pump?

Answer: If you’ve checked with a scan tool and it says there’s a problem with the oil pressure, then the problem is in the system. Of course, you need to check if you have enough oil in the system. Check the dipstick. Then, you need to confirm how much pressure you got. You may be dealing with a sensor problem, sending unit, oil pump, valve problem. One symptom with low oil pressure is the engine sounds more ‘metallic.’ In this case, you shouldn’t drive the car until you determine what caused the low oil pressure. You need to have the engine diagnosed.

Question: I have a 2000 Chevy Astro and base van. I was driving home on the freeway and at about 55mph (ca. 89 km/h) it lost all power. Now my lil psi gauge says 0psi, except when it's cold started. But soon as its warm it drops and stays at 0psi, except while accelerating. What might be the cause?

Answer: This may be happening if the engine is overheating, or the oil pump relief valve is faulty.

Question: I have a 2005 Jeep Cherokee 3.7L. After changing the oil, the amount increased. What should be checked in order?

Answer: Check the oil capacity for your model in your car owner's manual or repair manual. If there's too much in there it can affect engine performance. Drop some of the oil if necessary.

Question: I have a Toyota Yaris 2006. It suddenly showed a low oil indication, and we stopped and towed the car to the garage. But a mechanic is saying that there is some fault with the engine. Can low oil pressure affect the engine that quickly?

Answer: If the oil level was low – which is what the warning indicator says – probably you could’ve added some oil and continue on with your journey. This could’ve been caused by a leak or simply that you needed to add some oil as is usually the case with an engine from time to time. If the warning indicator was about “Low Oil Pressure”. This was a more serious warning. Low oil pressure can seriously damage the engine. But low oil pressure can be caused by several factors, one of them can be engine mechanical problems. In this case, there could be worn components, like bearings or main bearings, that needs a major repair, a blockage in the lubrication system, a failing oil pump, for example. So it is possible that mechanical problems caused low oil pressure, not the other way around. Since you didn’t continue driving the car when the warning appeared, I don’t think you caused the problem. But the fault needs to be diagnosed to see what happened.

Question: What does it mean when your oil pressure drops from 40 psi to 20 psi?

Answer: Make sure there is enough oil; check the oil for contamination. If you haven't changed the oil filter, replace it when changing the oil. You can have a problem with the oil sending unit. The best way to diagnose it is to connect an oil pressure gauge and confirm that you actually are losing pressure, before replacing components.

Question: I have 2018 Chrysler Pacifica, how do I know if I have an oil leak?

Answer: This other post can help you diagnose a leak:

© 2018 Dan Ferrell

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