Engine lubrication systems can be classified according to the nature of their sumps. A sump is an oil pan that is placed at the base of an engine that contains the lubricating oil. Since there are two types of sumps, dry sumps and wet sumps, engine lubrication systems are also classified into wet sump lubricating system and dry sump lubricating system.

Advantages:

• The design if a wet sump is simple. There is no need of a separate container and lines to store and carry the lubricating oil around. This relieves a lot of space and weight in the automobile.

• The cost is cheaper than the dry sump system, because it has comparatively less number of parts.

• Easy to setup and practical to use.

Wet sump systems can be classified into three types

1) The splash system
The splash system is out of use in automobiles today and is used only in miniature engines like lawn movers and in outboard marine operations. In the splash lubrication system, lubrication oil is stored in the sump below the crank case and is splashed upwards for lubrication. When the oil is splashed up, it mixes with air and becomes a fine mist and it lubricates several parts of the engine like the piston, cylinder walls, piston heads etc. To make the splash happen, a dipper is connected to the connecting rod bearing caps. When the crankshaft rotates, the dipper dips in the sump and splashes the oil upwards.

2) The splash and pressure system

In the splash and pressure system some parts of the engine are lubricated by the splash and pressure system, while some parts are lubricated by a pump through pressure.

The oil from the pump first enters the galleries of the engine. From there, it flows to the crankshaft and camshaft bearings. The main bearings have oil-feed grooves. These send the oil into drilled passages in the crankshaft. The oil thus flows through these passages to the piston pin bearings. This is the process by which a part of the engine is lubricated by pressure from a pump.

The cylinder walls are lubricated by oil that is splashed up from below. Some of the engines also use troughs under the connecting rods that are supplied by small nozzles while deliver oil under pressure from the pump. The oil stream delivered by the nozzles increase in force when the speed of the automobile increases. This causes a much heavier splash and the necessary parts are lubricated well.