An oil leak in a car engine can be caused by several factors, including:

• Leaking oil filter: The oil filter is one of the most common causes of an oil leak. If the oil filter is not installed properly or the seal is damaged, it can cause a leak.

• Bad gasket: Gaskets act as seals between different vehicle components, and many of them can wear out over time and lead to an oil leak. Some of the gaskets that could be to blame include the valve cover gasket, cylinder head gasket, timing cover gasket, and oil pan gasket.

• Worn seal: Crankshaft seals can be found at both ends of the crankshaft, and if they dry out, crack, or get damaged, they can lead to leaks.

• Loose drain plug: A damaged or worn-out drain plug can cause an oil leak. This type of leak is usually caused when the whole oil drain plug or the oil plug sealing is not replaced after every oil change.

• Damaged oil pan or gasket: The oil pan and gasket are located at the bottom of the engine and can be damaged by road debris, leading to a leak.

To avoid oil leaks, it is important to change the oil and oil filter regularly and ensure that they are installed properly. It is also important to check the oil level regularly and look for signs of leakage, such as oil puddles under the car or a burning smell while the engine is running.