Should the Oil Filter Be Replaced When Changing Engine Oil?
3 Answers
Changing the engine oil requires replacing the oil filter. Here are the relevant details: 1. Function of the oil filter: The oil filter removes impurities from the oil circulating in the lubrication system. After the engine runs for a period, it generates some impurities. 2. There are mainly two types of impurities: One is metal particles worn off from engine components during operation, and the other is black sludge-like organic matter produced by chemical reactions when the oil is exposed to high temperatures during engine operation. These impurities mix with the oil and circulate through the lubrication system.
Last time at the auto repair shop, I saw a case where the owner only changed the engine oil but not the oil filter, and the engine started making strange noises after just 3,000 kilometers. The oil filter is like a mask—once the filter paper pores are clogged with metal shavings and sludge, it becomes completely ineffective. Mixing new oil with old, contaminated oil is equivalent to not changing it at all. A mechanic I know said that an oil filter costs at most a few dozen dollars, but trying to save this small amount could lead to spending thousands on engine repairs. There was a car in their workshop where a ruptured filter caused oil passage blockage, ultimately requiring a major overhaul of the turbocharger. It’s recommended to replace the filter every time you change the oil, especially for turbocharged models. If left unchanged for a long time, metal particles settling in the oil pan will cause the oil to degrade prematurely.
Structurally, the oil filter contains folded filter paper inside, designed to capture particles larger than 5 microns. When it becomes overloaded, the bypass valve opens to allow unfiltered oil to enter the engine. Currently, full synthetic oils generally have a lifespan of 10,000 kilometers, but the filter cannot last that long. I've personally seen old filters cut open, with the filter paper caked into hard blocks by sludge. My experience is: conventional mineral oil requires a filter change every 5,000 kilometers, and even full synthetic oil shouldn't exceed 7,000 kilometers. Especially for city driving with frequent start-stop cycles, carbon deposits and particles can be three times more than during highway driving.
