Internal combustion engines depend on reliable engine lubrication. Inside the engine, lubrication ensures a reduction in friction between the individual engine components. Lubrication also ensures that heat and dirt particles are removed from the combustion engine.

How does engine lubrication work?

The engine lubrication system of modern four-stroke engines is designed as a pressure lubrication system. In contrast to other lubrication systems such as fresh oil lubrication, the oil is in a closed circuit. A pressure pump generates the necessary pressure to deliver the engine oil and reliably lubricate all lubrication points.

How does the oil circuit in the engine work?

In the oil circuit of the engine, an oil pump draws the oil from the oil pan. Via the filter, the engine oil reaches the lubrication channels and the lubrication points. Moving parts inside the engine partly ensure that the oil is nebulized. The lubricating oil then drips back into the oil pan. In the case of dry sump lubrication, several pumps can be used.

Components of the lubrication system in a car:

• Oil pump: the oil pump delivers the engine oil to the lubrication points inside the engine with sufficient pressure. Oil pumps in cars are usually driven directly by the engine.
• Oil pan: The oil collects in the oil pan after it has passed through the engine block. In the case of forced-feed lubrication as wet-sump or dry-sump lubrication, it is drawn in here.
• Oil cooler: An oil cooler provides additional cooling for the engine oil. The component is directly integrated into the circuit for the engine oil and connected via oil hoses or oil lines.
• Oil filter: The oil filter filters contaminants out of the oil after it has been drawn in by the oil pump. This prevents dirt particles from reaching the engine’s lubrication points.
• Oil dipstick: The dipstick allows the user of the car to check how much lubricant is in the engine. To do this, the dipstick can simply be pulled out of the engine compartment.
• Oil pressure switch: An oil pressure sensor or oil pressure switch checks whether the pressure in the lubrication system is as specified. If the oil pressure is not correct, an indicator lamp lights up.

What needs to be lubricated in the engine?

In internal combustion engines, lubrication of all moving engine parts is mandatory. Almost all parts inside the engine are movably connected or rotatably mounted at certain points. During engine operation, friction occurs between the components, which can be minimized by effective lubrication. This reduces wear and defects. The moving engine parts are supplied with engine oil via lubrication points or by swirling. These include, for example, the camshaft bearings and the crankshaft. The connecting rod bearings also require reliable lubrication. The pistons in the engine cylinders must also be supplied with oil for cooling and to minimize friction.

What lubrication systems are there?

Different lubrication systems are used in cars, depending on the engine design. Internal combustion engines as four-stroke engines usually have a pressure lubrication system as wet sump lubrication or dry sump lubrication. In this type of lubrication, an oil pump delivers the engine oil to the lubrication points. The oil that drips into the oil pan is fed through an oil filter and returned to the lubrication system.

Recirculating pressure lubrication as wet-sump lubrication

In wet-sump pressure lubrication, the lubricating oil dripping from the engine collects in the oil pan. Here, the oil cools down and returns to the lubrication points via the oil pump and the oil filter. Most cars with four-stroke engines have wet-sump lubrication.

Engine lubrication as dry sump lubrication

Dry sump lubrication is often installed in engines of sports cars. In this form of lubrication, a pump draws off oil directly from the oil pan. The lubricating oil collects in a reservoir. This means that enough oil is available for the engine under all driving conditions.

Lubrication of two-stroke engines

Two-stroke engines burn the lubricant together with the fuel in the form of mixed lubrication or fresh oil lubrication. Both substances mix directly in the fuel tank in the case of mixed lubrication. In fresh oil lubrication or consumption lubrication with fresh oil automatic, a pump mixes the necessary lubricant with the fuel.

Detecting lubrication defects

All components of the lubrication system are exposed to constant stress during operation of the car and can break down. Defects in the lubrication system should always be taken seriously. An insufficient supply of oil to the lubrication points leads in the worst case to capital engine damage.

The most common defects in the engine lubrication system:

1. Oil pump defective: If the pump for the engine oil is defective, this is usually manifested by a drop in oil pressure. The oil pressure indicator lamp lights up, and sometimes an error message also appears on the vehicle display. In some cases, the oil pressure control lights up for longer than usual after the engine is started if the pressure pump is working incorrectly.
2. Oil system leaks: Leaks in the oil system cause oil to escape from the oil circuit. Often, the engine oil visibly escapes from a defective connection, a broken hose or a leaking oil cooler. The consequences can be an insufficient oil level in the oil pan and reduced oil pressure. A leak is not always visible immediately.
3. Oil pan damaged: The oil pan can be easily damaged due to its position under the car. Weathering can also cause wear and rusting through of the component. A damaged and leaking oil pan is usually manifested by oil stains under the car or oil on the vehicle floor. But a broken oil pan gasket can also lead to oil loss.