An oil filter, also known as an oil strainer, is used to remove impurities such as dust, metal particles, carbon deposits, and soot particles from engine oil, protecting the engine.
Oil filters are classified as either full-flow or split-flow types. A full-flow filter is connected in series between the oil pump and the main oil passage, thus filtering all the lubricating oil entering the main oil passage. A split-flow filter is connected in parallel with the main oil passage, filtering only the portion of the lubricating oil pumped out.
During engine operation, metal shavings, dust, carbon deposits oxidized at high temperatures, colloidal deposits, water, and other contaminants continuously mix into the lubricating oil. The function of the oil filter is to filter out these mechanical impurities and colloids, keeping the lubricating oil clean and extending its service life. An oil filter should have strong filtration capacity, low flow resistance, and a long service life. Generally, a lubrication system uses several filters with different filtration capacities-a strainer, a coarse filter, and a fine filter-connected in parallel or series in the main oil passage. (A filter connected in series with the main oil passage is called a full-flow filter; all lubricating oil passes through this filter during engine operation. A filter connected in parallel is called a split-flow filter.)
The coarse filter is connected in series with the main oil passage, making it a full-flow filter; the fine filter is connected in parallel with the main oil passage, making it a split-flow filter. Modern car engines generally only have a strainer and one full-flow oil filter. The coarse filter removes impurities with a particle size of 0.05mm or larger from the oil, while the fine filter removes finer impurities with a particle size of 0.001mm or larger.
