Oil Leaks When Car Is Parked: 8 Causes

A damaged oil pan seal or drain plug is the most common cause of oil leaking when car is parked or off. Oil can also leak from the oil pressure sending unit, oil pump o-ring, oil filter seal, or engine seals and gaskets if the car sits at an angle for too long. Parking uphill increases the chance of oil leaks. Clogged PCV valves cause high crankcase pressure and can push oil past seals. Regularly inspecting seals and gaskets can help prevent leaks.

If you’ve ever come across the sight of a puddle of greasy-looking brown liquid under your car after it has been parked for a while, then you’ve probably been a victim of an oil leak.

Oil leaks can be a major cause of concern for car owners when their vehicle is parked. It can be difficult to determine the cause of the oil leak when the car is parked.

But don’t worry, I’m here to tell you that oil leaks when a car is parked don’t have to be hopelessly mysterious. With a little bit of troubleshooting, you can pinpoint the source of the leak and take action to fix it. 

Bonus Read: 5.3L engine common oil leaks

Some Key Insights for You
  • Oil leaks when parked can come from many places – oil pan, drain plug, oil filter, seals, sensors, valve covers. Regular inspection helps catch issues.
  • Engine heat when running causes gaskets and seals to expand, reducing leaks. When parked and cooled, leaks can occur more easily.
  • Oil leaks often start small but can become serious if ignored. Identify the exact source of leaks by thorough cleaning and using talcum powder or UV dye.
  • With high mileage engines, upgraded viscosity oil can help reduce leakage through increased clearances.

My Personal Experience With Oil Leaking When Car Is Parked

Just last month, my coworker John came to me concerned about an oil leak on his 2015 Toyota Camry. He showed me the small puddle forming on his garage floor whenever the car was parked.

I had him pop the hood so I could inspect the engine. I noticed oil dripping from the valve cover and suspected the gasket was worn. I confirmed this by removing the cover and seeing the old brittle gasket.

I advised John to replace it with a Toyota OEM gasket set. He ordered the parts and I walked him through the replacement process – cleaning the surfaces, applying sealant, torquing bolts to spec. The repair only took an hour and completely fixed his leak.

Can You Drive With An Oil Leak?

The short answer is, yes, you can drive with an oil leak. However, there are some conditions that must be met in order for this to be a safe option.

First, you need to make sure that the oil level is between the upper and lower marks on the oil dipstick. You can do this by removing the oil dipstick, wiping it off, and then reinserting it. If the oil is too low, it can cause serious damage to your engine.

The next thing you should consider is the oil pressure from the oil pressure gauge on the dashboard.

You should make sure the oil pressure is within the manufacturer’s specifications. If there is not enough oil pressure, it will affect the lubrication and damage the crankshaft bearings.

If the oil level is low or the pressure is low, then you should definitely not drive with an oil leak.

The oil is necessary for keeping the engine lubricated and running smoothly. Without the proper amount of oil and pressure, the engine will overheat, seize, and can cause serious damage. 

To learn more, you can also read my guide on the consequences of changing oil after 2 years.

Visual Inspection Of Oil Leak

Before you investigate the reasons behind an oil leak when the car is parked, you should first confirm that it is actually engine oil and not something else. Oftentimes, people mistake engine oil, transmission oil, and coolant.

So, if the color of liquid leaking from car when parked is:

  • Brown or black: It indicates engine oil.
  • Blue, orange or green: It indicates coolant.
  • Reddish or red-brown: It indicates transmission oil.
  • A very light pale or Golden color: It usually represents brake oil oil power steering fluid
  • Golden color: It represents power steering fluid. It also gets dark brown/black with time.

Causes Of Oil Leaks When Car Is Parked

Here are the causes of oil leaks when a car is parked:

1. Gasket Of Oil Pan Is Damaged

The oil pan is a low point of the engine where all oil runs downhill when the engine is not running.

An oil pan gasket is a thick rubber seal that sits between the oil pan and the engine block. Its job is to keep oil from leaking out of the oil pan.

Over time, the gasket can become worn out and start to break down due to the engine’s heat and pressure.

This will allow oil to escape from the pan when the car is parked. The oil will then leak onto the ground underneath the car. 

How does oil pan gasket damage and cause oil leak?

The rubber gasket can become worn or damaged due to a variety of reasons, including:

  • Rough roads: Driving on rough roads can cause the oil pan to vibrate, which can lead to the gasket becoming worn or damaged.
  • Debris: Debris can get into the oil pan and cause damage to the gasket.
  • Age: Over time, the gasket can become brittle and worn.

You should make it clear that as the oil pan is the low point of the engine, an oil leak from somewhere above will eventually hit the seam between the oil pan and the engine block and migrate all the way around, making it look like a oil pan gasket leak. 

How to fix leaking oil pan gasket?

Always use an OEM-recommended oil pan gasket. Don’t go for cheap aftermarket alternatives.

To install a new oil pan gasket, use the engine degreaser to clean the mating surface of the oil pan, and remove foreign particles, such as RTV, dirt, and oil. If the mating surface of the oil pan is not cleaned properly, it will not seal the gasket.

I would recommend this engine degreaser to clean the mating surface of the oil pan. Use a lint-free towel to clean the mating surface of the oil pan before installing the gasket.

If the oil pan is chrome-plated, brush out the drain hole threads to clean any leftover flakes that could start a leak. You may also need to tap around the bolt holes of the oil pan.

After cleaning the oil pan mating surface, apply a thin bead of RTV silicon sealant to adhere the new oil pan gasket to the oil pan. Make sure that you don’t apply too much sealant. Mount the gasket to the oil pan. Allow some time for the adhesive to set. Test for slippage with light pressure. If the gasket moves, allow more time.

2. Warped Mating Surface Of Oil Pan

Warped Mating Surface Of Oil Pan

In addition to the oil pan gasket, you should check the bolts and mating surface of the oil pan if the oil leaks when the car is parked.

The mating surface of the oil pan is the area that fits against the engine block. If this surface becomes warped or cracked, it can no longer make a tight seal with the engine block and result in oil leaking out.

Furthermore, the bolts of the oil pan can also damage due to corrosion. This occurs when the metal of the oil pan is exposed to moisture, either from rain or condensation.

The moisture will cause the metal to rust and weaken, leading to cracks or holes in the oil pan. In some cases, this can cause the bolts to come loose as well.

Another possible cause of oil pan damage is poor installation. If the oil pan is not securely fastened to the engine block, it can cause the bolts and mating surface to become loose over time. This can lead to leaks, as the oil will start to seep out from the gaps in the mating surface. 

How to diagnose warped oil pan?

If the mating surface of an oil pan is warped, it can be checked with a straight edge. Lay the straightedge lengthways along the flange that contacts the engine block.

Then take a feeler gauge and see if you can get any feeler gauge to slide in any spots under the straight edge.

Make sure that the gap between the straightedge and the oil pan is not greater than 0.1mm. If you find it warped, you’ll have to bend, pound, or hammer the oil pan till it’s straight again.

checking the flatness of engine oil pan mating surface to fix oil leak when car is parked

Lastly, when tightening the bolts, you should follow the torque specifications by the manufacturer. Avoid overtightening the bolts.

3. Loose Drain Plug Of Oil Pan

drain plug of oil pan

The drain plug is threaded into the oil pan, and when tightened, it creates a seal. This seal prevents oil from leaking out of the pan.

When the drain plug of the oil pan gets loose, it can cause oil to leak from the pan. When the car is parked, the oil can slowly seep out of the pan and form a small puddle below the engine.

Fortunately, preventing a loose drain plug from causing an oil leak is relatively simple.

It is generally recommended to replace the washer of drain plug whenever you drain out the old oil as the seal of the drain plug gets damaged due to the oil sludge.

It is difficult to find a suitable seal for the drain plug. The metal drain plug has usually a sealing metal washer instead of a rubber seal.

Furthermore, you should use a torque wrench to ensure that the drain plug is tightened to the correct specification for your specific car model.

4. Oil Filter Is Loosen Or Misaligned

If the oil filter is not properly tightened or misaligned, it can lead to oil leaks when the car is parked. An oil filter is a very messy area of oil leakage. If it is ignored, oil can eventually get on the serpentine belt system and deteriorate the belt.

When the oil filter is loose, a gap is created between the oil filter and the engine. This gap will allow oil to bypass the filter and leak out. This is because the oil pump sends oil through the oil filter to the engine. If an oil filter is loose, the oil pressure can push the filter off, causing oil to leak out of the opening.

The configuration of the oil filter fitting depends on the type of engine. In some engines, an oil filter is fitted into the engine block through an adapter. In other engines, the oil filter is directly bolted into the engine block.

I have shown both configurations of the oil filter in the picture below:

Configurations of oil filter

Furthermore, if an oil filter is not the OEM and the correct size, the pressure of the oil may be too strong for the filter, causing it to break or become loose.

Aftermarket oil filter of different size will be misaligned and slightly off-center from where it is supposed to be.

This will cause oil to leak out of the filter, making a mess and potentially damaging the engine if oil levels get too low. 

Furthermore, while replacing the oil filter, most people forget to remove the old gasket that usually sticks to the engine block. 

If you accidentally use two gaskets while installing the oil filter, they will blow out due to excessive pressure and cause oil leakage when a car is parked.

So, you’ve to make sure that there is only one gasket of the oil filter while installing it. You should remove the old gasket.

You can check out the below video from 5:00 time. That guy has explained in detail about the leakages through the oil filter.

5. Valve Cover Gasket Is Damaged

Valve cover

A valve cover gasket is a seal that goes between the valve cover and the cylinder head of a vehicle’s engine. The valve cover gasket is there to prevent oil from leaking out of the engine. The valve cover is also called a rocker cover.

In the illustration above, I have shown two pictures. One with the valve cover placed, and the other with the valve cover removed. In the picture with the valve cover, you can see camshafts that are enclosed in a cylinder head.

Oil is needed to lubricate the camshafts to reduce the friction between cams and the valve mechanism that is driven by the cams.

When the gasket is intact, the valve cover is held down securely and oil is prevented from leaking out.

However, over time, the gasket can become worn or damaged. The valve cover gaskets can become brittle and break down due to age.

Furthermore, excessive heat can cause the valve cover gasket to expand and contract, leading to cracks or tears.

When a valve cover gasket gets damaged, it can no longer keep oil from leaking out. When a car is parked, the oil will slowly drip out of the engine and onto the ground. 

Moreover, some engines have plastic valve covers instead of metal. The plastic valve covers develop hairline cracks over time from the heat involved in the engine compartment, expansion, contraction, etc. These often have to be replaced along with the gaskets.

6. Damaged Seal Of Crankshaft and Camshaft Position Sensors 

oil leaking through crankshaft sensor seal

Camshaft and crankshaft sensors are responsible for monitoring the position of the crankshaft and camshaft and are responsible for the proper functioning of the engine. They are located in the engine, and when the engine is running, the sensors send signals to the ECU.

Also Read: What happens when cam phasers go bad due to low engine oil

The crankshaft and camshaft position sensors are both sealed with rubber O-rings. These O-rings keep oil from leaking out of the engine. Over time, these O-rings can become brittle and dry out, which can cause them to crack or break. When this happens, the oil that is inside the engine can start to leak out, resulting in an oil leak.

The camshaft sensor is located near the top of the engine i.e. close to the camshafts. Usually, you’ll find a camshaft sensor around the valve cover.

As I explained above, the oil flows over the camshafts to lubricate them. If the seal of the camshaft sensor is damaged, the oil will leak through the engine.

Similarly, the crankshaft position sensor is located closer to the crankcase (bottom part) of the engine. A crankcase is a part of the engine block where the crankshaft is located. Engine oil flows through the crankcase to lubricate the crankshaft. 

Somewhere around the crankcase, the crankshaft sensor is located. If the o-ring of the crankshaft sensor is damaged, the oil will leak through the crankcase.

location of camshaft and crankshaft sensor

7. Damaged Rear Main Seal

rear main seal of engine

The rear main seal is located at the rear of the engine, where the crankshaft comes out of the block. The rear main seal, located between the engine and the transmission, is a critical part of your car’s engine. It is responsible for keeping engine oil from leaking out. 

The rear main seal is also a low point of the engine where the oil collects and can leak through when the seal cracks.

If you see engine oil dripping from the flywheel area of the engine or bell housing of the transmission, the chances are that the rear main seal is damaged.

The rear main seal is made out of rubber, which can start to wear out over time. It can also become brittle, dry, harden and crack due to extreme temperatures, or it can be damaged by debris in the oil. 

8. PCV System Is Not Working Properly

The Positive Crankcase Ventilation system (PCV) is a critical part of your engine’s emission control system.

It helps keep the pressure inside the engine at a safe level by removing the oil vapors that build up pressure in the crankcase. 

PCV system works by sucking out the oil vapors through a hose via a PCV valve and sending them back through the intake manifold.

The PCV valve:

  • Closes slightly to reduce airflow at low RPM (idle), when the vacuum is high.
  • Opens more to increase airflow at high RPM, when the vacuum is low.

If PCV valve is stuck closed, the pressure of oil vapors will build up in the crankcase which will cause oil to leak from the engine seals under high pressure.

How to spot bad PCV valve?

To test if the PCV valve is stuck closed, you can remove the oil filler cap and place the paper on its opening. If it holds the paper against its opening, it means that the PCV valve is malfunctioning.

Why Oil Only Leaks When Car Is Parked?

The main reason why oil can only leak when your car is parked is that when an engine is running, the gaskets and seals are heated up and expand, creating a tight seal that keeps the oil from leaking out.

However, when the engine is turned off and the vehicle is parked, the gaskets and seals start to cool down and contract. This can cause them to become brittle and more prone to cracking, which can lead to leaks.

Another factor that contributes to oil leakage is the age of the engine. Over time, the seals and gaskets of the engine become worn and brittle, thus making them vulnerable to leakage.

If you notice that your car is leaking oil only when it is parked, it may be time to consider replacing the seals and gaskets to prevent any further leakage. 

So, in short, when the engine is running, the oil is pressurized and flows through the engine to lubricate its various components.

The oil pump, which is powered by the engine, keeps the oil circulating at a consistent pressure. When the engine is turned off and the vehicle is parked, the oil settles down and can pool in certain areas. This will cause oil leakage.

Furthermore, as the engine gets older i.e. have crossed over 100,000 miles, it is generally recommended to use slightly use thicker oil. For instance, if you have been using 5w20 before, you can 5w30 oil instead of 5w20.

When the engine gets older, its components wear out, and the clearances between the engine’s components increase.

If the oil is thinner, it will leak through the engine. So, in those cases, engine oil of higher viscosity grade is recommended. You can read my guide on the best oil for cars with over 200000 miles to learn more.

How To Spot The Cause Of Oil Leakage From The Car?

If oil is leaking from the car when parked uphill, you should bring the vehicle onto flat ground, and jack it up. Then place a piece of cardboard underneath the vehicle for a day, and see where the oil is.

To identify oil leak spots on your car, you must clean it all up with an engine degreaser and check it a few times once it’s clean.

This is because oil leaks can start higher up and dribble down, making it look like it is leaking from somewhere else. The wind current from driving can also push oil far from its point of origin.

So, after a thorough cleaning, you can spray talcum powder all over. The source will appear as a brown spot in the white talcum powder.

You can also add ultraviolet dye to the oil, run the engine with it and look for the leak with a UV light.

Final Thoughts

Oil leaks can seem hopelessly mysterious when a car is parked, but with some diligent troubleshooting the source can be identified.

Regular inspections and maintenance of seals, gaskets, sensors, and the PCV system are key to preventing leaks. If a leak does occur, thoroughly cleaning the engine and using techniques like talcum powder or UV dye can reveal the origin.

With age, higher viscosity oil may help reduce leakage. Ultimately, catching leaks early and repairing the source promptly reduces the chance of extensive engine damage.

Consistent care for your engine’s lubrication system keeps it running smoothly for years to come.

Oil Leaks When Car Is Parked: FAQs

How much does it cost to fix an oil leak?

The cost of fixing an oil leak can range from relatively affordable to quite costly, depending on the severity of the leak and the type of car you own.

If it’s a minor leak like changing the drain plug or gasket of the oil pan, you may be able to repair it yourself.

If you’re lucky, and the oil leak is caused by a oil filter that needs to be replaced, the repair is likely to be much less expensive.

However, if it’s a major leak like a valve cover gasket, it’s best to consult a professional automotive technician. 

Is an oil leak serious?

A major oil leak can cause your oil level to drop faster than normal. This can lead to other issues with your vehicle, such as a worn timing chain, camshafts, or even piston and cylinder issues. In some cases, a major oil leak can cause your engine to seize up. 

What is the cause of oil leaks when a car is parked?

Oil leaks when a car is parked can be caused by a variety of issues, such as a faulty oil filter, worn-out gaskets, or a cracked oil pan. 

How do I know if my car is leaking oil?

You can tell if your car is leaking oil by visually inspecting the area around the engine for any signs of oil. You can also look for puddles of oil when parking or driving your car and check the oil level on the dipstick. 

Some First Hand Experiences Shared By Users In Different Communities

Our team conducted research across various online communities, forums, and subreddits to gather user comments and opinions on “oil leaking from car when it is parked”.

User 1 says:

My 2017 Chevrolet Malibu had an oil leak that I discovered through a small puddle under the car. It was a faulty rear main seal. A bit expensive to fix, but it solved the problem.

User 2 says:

Had a bit of a scare with my Subaru Impreza when I noticed oil leaking. It was due to a damaged head gasket, evidenced by white smoke and oil under the car. Repaired it, and it’s been running well since.

User 3 says:

Experienced an oil leak in my Nissan Sentra. The issue was with the oil drain plug. It wasn’t tightened properly during the last service. I spotted the problem from oil spots on my driveway. A quick fix, and it was sorted.

User 4 says:

Had an oil leak in my Lexus ES. The issue was a bit tricky – it was the camshaft sensor seal that was leaking. Found out after seeing oil traces on the engine. Got it repaired, and the car’s been great since.

User 5 says:

Recently found an oil leak in my 2016 Honda Accord. Noticed some oil spots on the driveway. After inspecting, I realized it was the oil pan gasket that had worn out. Replaced it at a local mechanic, and it’s been fine since.

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