Car oil leaks: causes, consequences, and solutions

Car oil leaks: causes, consequences, and solutions

Engine oil performs very important functions. It creates a film on the surface of the parts to prevent their wear, removes heat from the moving elements, and protects them from corrosion. In addition, it cleans the engine. Lack of lubricant is dangerous for the motor. In this article, we look at why leaks may occur, tell you where to look for the fault, and find out whether a car leaking oil is safe to drive.

Why is my car leaking oil?

 The most common causes of oil leaks are: 

Worn seals

Gaskets, seals, and O-rings are usually made of rubber, which over time loses its durability and becomes less elastic. As a result, the car starts leaking oil in the area of ​​the mating surfaces sealed by these elements.

Why is my car leaking oil


  • Visually inspect the valve cover. If you see lubricant stains in the area where it contacts the cylinder head, this is an indication that the gasket has deteriorated and needs to be replaced.
  • Check the junction between the engine block and the cylinder head: a leak here may occur as a result of engine overheating, which leads to deformation of the engine block and cylinder head, and breakdown of the gasket.
  • Unscrew the cap of the coolant reservoir and check whether there are any traces of lubricant in it. If there are, this also indicates the loss of tightness at the junction between the engine block and cylinder head.
  • Inspect the oil filler neck. White foam on it is a sign that coolant is getting into the lubrication system.
  • Replace the cylinder head gasket. Bring your car to a mechanic for this, as the repair probably won’t be limited to the installation of a new gasket; grinding of the mating surfaces will be required as well.
  • Examine the ignition distributor mounting seat. If a leak is detected, replace the oil seal or O-ring.
  • Inspect the oil filter. If your car is leaking oil from under its seal, try to fix the problem by tightening the part with more force. If this doesn’t help, replace the component.
  • Check the crankshaft oil seals. Their failure can be caused by increased crankcase pressure, or installation errors. Mount new parts. Note: You will need to disassemble the engine to do this, so it’s a good idea to replace the camshaft oil seals at the same time.

Check the crankshaft oil seals

Increased pressure in the system

Accumulation of dirt and impurities can reduce the throughput capacity of individual sections of the lubrication system, which leads to a local increase of pressure. This may also be the result of clogging of the crankcase ventilation components, which leads to exhaust gases getting into the lubrication system. As a result, oil is squeezed out through seals and joints. Sometimes the problem is caused by an excessive amount of lubricant, and its high viscosity.


  • Measure the pressure in the lubrication system using a pressure gauge. If it’s higher than normal, proceed to the next step.
  • Remember when you last changed the oil. If the vehicle has covered about 15,000 km since then, replace the lubricant and the oil filter.
  • Make sure you use the product with the viscosity recommended by the manufacturer. Higher viscosity may increase the pressure.
  • Flush the lubrication system. To do this, pour a special additive into the oil filler neck, start the engine and let it idle for a while. After that, drain the fluid, replace the filter and pour in the new oil.
  • Check the oil level. If it exceeds the level prescribed, remove the excess amount using a special vacuum extractor, or drain it through the drain plug.
  • Remove and inspect the pressure relief valve. Clean it of dirt. Check if the locking mechanism moves freely. If it’s seized up, replace the valve or the entire pump assembly.
  • Warm up the engine to operating temperature. Remove the oil filler cap and cover the hole with your hand. Ask an assistant to press the accelerator pedal several times to increase the engine speed to 2,000–2,500 rpm. If you feel pressure increase in the system as the car revs up, then the crankcase ventilation system is faulty. Bring your car to a garage to have it repaired. The specialists there will clean the components, and, if necessary, replace the PCV valve and oil catch can.

Check the oil level

Installation errors

Improper tightening of bolts and an incorrect tightening sequence can cause warping or cracking of the gasket. In addition, using sealants and adhesives to try to fix the seal can damage it.


Replace the seals and gaskets. Observe the manufacturer’s specified tightening torques. Screw in the fasteners according to the layout provided in the vehicle’s service manual. When installing oil seals, use specialised tools.

Mechanical damage

This can be caused by the ingress of foreign objects, or hitting an obstacle, which the oil pan is most vulnerable to.

Mechanical damage


  • Seal the crack by means of cold welding.
  • Take your car to a garage to have the oil pan welded.
  • Install an oil pan guard. If you often drive off-road or use your vehicle on poor quality roads, this will help you avoid a lot of problems.

Loose fasteners

As a result of driving on poor-quality roads and excessive vibrations of the car due to, for example, worn suspension components, some fasteners can become loose. You may find the car is leaking oil from under them.


Tighten the clamps and fasteners. Replace them if necessary.

Why a car leaking oil is dangerous

Due to the lack of lubricant, wear of mating parts increases. First of all, this adversely affects the condition of the valve stem seals, which further exacerbates the problem. The oil, already at too low a level, gets into the engine cylinders and burns there. The further lack of lubrication leads to the destruction and seizure of the camshaft and crankshaft, as well as of the engine pistons. In some cases, the connecting rods may break as a result of overheating.

In addition, if your car is leaking oil, the engine block itself gets contaminated, and dirt accumulates on it. This compromises the heat exchange processes, increases the load on the engine, and can cause it to overheat. The lubricant can accumulate in spark plug wells, which causes malfunctions in the ignition system. In addition, oil can destroy the insulation of wires under the bonnet, and clutch elements; it also can soften rubber mounts, seals, and interfere with plastic parts.

If my car is leaking oil, can I drive it?

If the leak is severe, for example if the oil pan is punctured, you must not use the car. It’s best to call a towing service. In case of minor damage, you can try to repair it with a sealant or by cold welding. On the way to the garage, be sure to constantly monitor the lubricant level. If it gets too low, top up the fluid to the required level to prevent oil starvation of the engine parts.

If my car is leaking oil, can I drive it

Is it possible that a car won’t start because of an oil leak?

An oil leak does not usually interfere with the engine starting. But in some cases, for example if the car is equipped with an oil level sensor and the level has reached a critical minimum, the electronic control unit may prevent the engine from starting.


The service life of an engine directly depends on the lubricant level. Therefore, any leaks are dangerous. They should be fixed as soon as they are detected. After all, repairing a car that is leaking oil is always cheaper than overhauling or replacing the engine.


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