Why Does My Car Leak Oil When Parked?

Finding an oil spot underneath your car can have you asking, “Why does my car leak oil when parked?” There are many reasons why your car could leak oil after it’s been sitting for a while. Tracking down the cause, however, doesn’t have to be a chore.

Instead, you can use this guide to systematically go through the possible culprits leaking oil.

Chances are you’ll find the reason your car leaks oil when it’s parked sooner or later.

Even if you find the leak but aren’t sure how to fix it, you can save a lot of time and money by being able to tell your mechanic where the issue is coming from.

If you fix something in the list below and want to check if your car is still leaking, you can easily put a piece of cardboard beneath your vehicle’s front end after you park it. If you find more oil on that cardboard in the morning, it’s time to check out the next possible culprit on the list.

10 things that could cause the car to leak oil when parked

The important thing to remember when you’re looking for the source of an oil leak is that your engine requires more oil to replace what it lost. If you don’t keep enough oil in the engine, the critical lubrication it provides can cause extensive and devastating failure.

To avoid even more costly fixes, be sure to check your oil daily and top it off as needed. Small leaks won’t make your car lose a lot of oil in a few days but if there’s enough oil on the ground to make up a decent-sized puddle, be sure to have an extra quart (or two) on hand.

Worn-out engine gasket

Engine gaskets are the seals that keep oil in your engine and ensure proper compression. Without these gaskets, your car is likely to puke out any oil left inside the engine itself.

Most engine gaskets are made from a semi-stiff material that flexes to take up the gap between metal components. Gaskets all over your vehicle wear out over time as that flexible material becomes brittle and stiff. It’s the same reason your car’s interior loses heat if you have decaying door seals.

One of the best ways to check for a worn-out engine gasket is to look at the engine block. If you see one or more spots where oil is leaking out of the engine and dripping down the sides, chances are it’s time to order a new engine gasket.

Replacing engine gaskets is one of the more expensive maintenance jobs besides replacing the entire engine itself. However, most engine gaskets last for years at a time under normal driving conditions.

Faulty oil filter

If you changed your own oil or just happened to get a bad oil filter, it could be the cause of your car leaking oil when it’s parked. Oil filters can leak if they have a puncture or don’t seal well against the engine block.

Most of the time, you’ll be able to visually identify if your oil filter is the source of the leak.

Oil will drip down the sides and may cover the filter as well as any engine parts surrounding it. If your oil filter is the cause, you’ll need to replace it and potentially the oil at the same time.

Damaged oil pan

Replacing the oil in your car is the least of your worries if you have a damaged oil pan. The most obvious fix is to replace the damaged oil pan with a new one, which means having to replace any gaskets and the oil that sits within them.

Oil pans get damaged in many ways. If you drove over something in the road and it struck the oil pan, causing it to leak, chances are the debris likely punctured the pan. Oil pans can also be damaged if you go over a bump and the suspension doesn’t lift the car’s body above it in time.

Offroading and landing on your oil pan after jumping your vehicle can also cause it to become damaged.

Cracked or worn-out engine block

Engine blocks are a giant hunk of metal filled with oil, and when they puncture or rupture, oil is bound to leak out. You can typically visually inspect your engine block to look for oil leaks, but sometimes they might be hidden beneath other components.

If your engine block is worn-out or cracked, there’s typically no better replacement than a new block. Replacing the engine block can be one of the most expensive repairs on a vehicle, but engines can last upwards of 150,000-200,000 miles or more with proper care.

Before you fork over thousands of dollars to replace your engine block, it can be worthwhile to track down why the block failed in the first place. Excessive use is one thing, but if there’s another cause for concern, you could be saving yourself the cost of an additional engine if you pinpoint it before installing the new engine.

Loose or damaged oil drain plug

Forget to turn the sink off all the way and you could be faced with a steep water bill from that excessive dripping. The same concept applies to oil drain plugs that aren’t tightened properly or have sustained damage.

Chances are your car’s oil pan will sustain damage before the oil drain plug, but anything is possible driving down the road. If something hits your vehicle in just the right spot, it could damage the oil drain plug to the point where it doesn’t seal properly.

A loose drain plug can happen when you get your oil changed. Checking the tightness of the drain plug can help you determine if it’s loose or not. While there might be some residual oil left on the block near the drain plug location, you shouldn’t see any fresh oil seeping from it.

High oil pressure

The temperature of your engine causes the oil to expand and contract. With high oil pressure, the compression within the engine can cause various failure points because the pressure rating exceeds the normal range.

High oil pressure most often occurs when you fill the engine with too much oil. While reducing the amount of oil within the engine can help reduce the pressure, it’s a good idea to check engine gaskets and seals to ensure there’s no lasting damage.

Overfilled oil

Overfilling your oil can cause just as many issues as not filling your car up with enough oil. This is why it’s critical to check your car’s oil level routinely, especially if you change your own oil. Be sure that your vehicle is on flat ground when you check the oil and don’t overfill it. In this case, less is more because it’s easier to add oil than it is to pull it back out of your vehicle.

Coolant mixing with oil

Many fluids help a vehicle drive down the road safely, but mixing them is rarely a good idea. If you find that you have coolant mixing with your oil, it’s time to shut the car off and call for a tow truck.

Coolant is the liquid that helps your vehicle’s engine stay at operating temperature throughout your drive. Oil works similarly, but provides more lubrication than it does temperature regulation. However, both liquids shouldn’t ever come into contact with one another.

If you find that you have coolant and oil mixing, you likely have a blown head gasket. This is the first cause of a car leaking oil that we discussed. Replacing an engine’s head gasket can be pricey and involve many other procedures, but it’s the only way to fix the issue of coolant and oil mixing.

Faulty rings or valve seals

Faulty piston rings can quickly cause high oil pressure and force your engine to consume more oil. As the rings fail, oil seeps into the combustion chamber. This is the last place oil should be if you want a working engine.

The same concept applies to valve seals. The valves in your car’s engine are meant to regulate the flow of air and fuel for optimal performance. If you introduce oil into the equation, everything goes haywire. If by chance, your engine continues to fire, you’ll want to drive immediately to a mechanic to diagnose the issue.

Missing or damaged filler cap

Oil can enter and exit your vehicle at multiple points. We often associate the oil pan, drain plug, and filter with removing oil to change it. However, you also have the filler neck and filler cap up top where you pour the new oil into the engine as one of the last steps of any oil change.

If your oil filler cap is missing or damaged in some way, it’s not creating the seal necessary to stop oil from leaking out. Without that cap, oil can slosh or seep out at any time. Most dealerships can order replacement filler caps for you at a reasonable price, making this one of the easier fixes if you find your car leaks oil when it’s parked.