Key Takeaways

  • A drain plug that’s not tightened down is the most common reason for oil leaks.
  • Some cars need O-Rings installed with their drain plugs.
  • Oil spills can stick to the side of an engine and give the illusion of an engine leak.
  • Overfilled engines can cause serious damage to an engine.
  • Valve covers are also common places for engine oil leaks.

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A car leaking oil after an oil change is a common occurrence usually due to an error on the mechanic’s part. But why exactly would it leak oil?

Some reasons that your car might be leaking oil after an oil change include:

  • A drain plug that’s not tightened down
  • An oil filter that’s not tightened down
  • An oil spill
  • A missing oil cap
  • A missing O-ring
  • A damaged pan gasket
  • A leaking valve cover
  • An overfilled engine

I’m a mechanic with 5 years experience diagnosing and repairing vehicles. I received my degree in automotive repair and I am ASE certified. I regularly diagnose and repair vehicles with the latest tools and technology. And I receive training on the most recently released automotive tools and technology.

Table of Contents

Oil Leaking From Car After Oil Change

As a lube tech it's common to see cars come back to the repair shop after an oil change job was just completed. Comebacks are more common than you think. While an oil change is a simple job, lot’s of different things can go wrong.

Oil leaks are very noticeable to the customer since it can stain their streets and driveways. So when an oil leak occurs after an oil change customers usually bring it back to the mechanic right away.

And it’s a good idea to do so since slow oil leaks have the potential to do major damage. Here are some of the reasons why oil may be leaking after you just have had your oil changed.

Drain Plug

The most common reason for an oil leak after an oil change is because the drain plug hasn’t been tightened down properly. Lots of times, mechanics will put the plug back into the service port and tighten it down with their fingers.

But they will forget to apply torque with a wrench or ratchet. When a mechanic does 15 oil changes a day it's easy to forget which step of the process you’re on and torquing down the drain plug might be the step that gets skipped.

Torquing down a drain plug is usually the last step before lowering the car. When the drain plug isn’t tightened down all the way a slow oil leak will develop.

To fix this, you can check the drain plug yourself by getting under the car and feeling the drain plug or bringing it back to the mechanic you just got it serviced from.

Oil Filter

A damaged or loose oil filter can also cause a slow but noticeable oil leak. Like the drain plug, it's easy to forget to torque to the oil filter once you screw it on. If you don’t add enough torque the seal between the engine block and the oil filter gasket won’t be complete and will cause oil to leak down the side of the oil filter.

As well, if the oil filter is damaged, this can cause a slow oil leak since the vehicle’s oil is rushed through the filter.  And if the threads of an oil filter aren’ intact it can cause an incorrect seal that will cause small leaks.

Replace the damaged oil filter with a new oil filter to fix this issue. .

Oil Spill

Some shops don’t have oil pumps that can directly pump oil into the engine. So the shops have to pour in the oil manually with a bucket and funnel. This process can be cumbersome and tiresome, meaning spills happen.

When an oil spill happens when pouring oil into a car, the oil trails down the whole engine block. The oil can sort of stick to the engine and start to form a path that the oil drips down from.

When oil sticks to the side of an engine it can start dripping down the side later causing what is interpreted as an oil leak. When really it's just some left over spilled oil.

Oil Cap

If you see oil leaks from down below you may want to check up top! Sometimes the oil cap can be left off at the mechanics.

Oil caps are quite often left off and the oil inside makes its way out of the top of the valve cover.

When an oil cap is left off, it can cause a slow leak or a major oil leak depending on the design of your engine.

That being said, if your oil cap is left off, the hood of your car will be covered in oil. To check if your oil cap is left off, just pop the hood and look where the oil cap should go. If it’s missing, you’re going to need to get a replacement oil cap.

Drain Plug O-Ring

Sometimes drain plugs come with washers that need to be installed along with the drain plug before it’s screwed into the oil pan. The washer goes around the drain plug and then the drain plug is screwed into the oil pan. If the washer is missing, motor oil can leak from the drain plug slowly. This type of leak will be very subtle but will still stain your driveway.

Oil Pan Gasket

A bad oil pan gasket can cause oil leaks after an oil change too. That’s because the new oil is more viscous and tends to stick to the side of oil pans more which can lead to an oil leak.

As well the torque applied to a drain plug can shift the gasket of an oil pan too causing a slow oil leak. Look around the sides of the oil pan for moisture to tell if you have an oil pan gasket leak.

Valve Cover Gasket

Previously, we spoke about the bottom of the engine with the oil pan but if you look at the top of an engine you may find an oil leak too. That’s because valve covers are common places for oil leaks to occur.

Lots of oil gets splattered at the top of engine heads and valve covers often leak because of this splattering.  Vibrations can cause the oil to leak out of the valve cover gasket and cause oil to leak onto your driveway or road when sitting overnight.

Overfilled Engine Oil

Another common cause of engine oil leaks after an oil change is an overfilled engine. When an engine is overfilled it can create excess pressure within the engine.

The excess pressure can cause oil to be forced out through seals and gaskets. The crankshaft can whip engine oil into a froth making the oil very thin.

This thin oil can force its way out of the engine through the engine’s weak points like seals and gaskets. This forcing of the engine oil through seals and gaskets can lead to an oil leak. Overfilled engines can also have oil forced up past the piston rings and find its way into the combustion chamber.

From here it will burn in the combustion chamber and cause lots of smoke that comes out of the tailpipe. This can result in fouled spark plugs, decreased engine performance, and increased emissions.

If you change your own engine oil make sure the level is good by checking it with a dipstick and following the vehicle manufacturer’s recommendations. These are the main reasons why an engine could be leaking oil after an oil change.

Most reasons are due to common mistakes made by the person doing the oil change. So be careful when changing the engine oil.

Doing An Oil Change Yourself

Doing an oil change yourself can be done but you must be careful. A lot of different considerations need to be taken into account when doing oil changes at home.

Some cars need special tools for the oil filters which not every household has lying around.

Vehicle manufacturer’s basically engineer their cars so the oil changes need to be done at the dealership.

They do this so the dealership can make more money on maintenance items like oil changes.

So if you do your oil change at home make sure you follow vehicle manufacturer’s recommendations.

Follow everything to a “T” from using the correct weighted oil to applying the correct torque to the drain plug.

Doing an oil change at home isn’t the task that it used to be.

It requires some doing, especially since you need to discard the oil properly. If you get caught discarding engine oil improperly you are looking at some legal recourse.

If you do change the engine oil at home and you notice a small leak make sure to check some of the items mentioned above.

It's most likely one of those things. Oil filters and drain plugs can become tricky objects to manipulate when you're flat on your back and not using a car lift.

And if you overfill your engine, empty out all the oil and start the engine oil change over.

Common Causes Of Leakage After An Oil Change

About The Author

Christopher Sparks

Christopher Sparks

Christopher Sparks has been servicing vehicles since 2012. After completing the automotive studies program at Camden County College, he was awarded an Associates's Degree in Applied Science. His first job was a lube-tech at Jiffy Lube, and is currently an independent B-Technician servicing vehicles for the United States Postal Service. Christopher is ASE certified and loves rebuilding engines.

Read more about Christopher Sparks