Is it necessary to replace the oil filter when changing engine oil?
2 Answers
When changing engine oil, it is essential to replace the oil filter as well. If you only change the oil without replacing the filter, the new oil will mix with the old oil trapped in the used filter, compromising the lubrication effectiveness of the fresh oil. The oil filter is designed to remove impurities such as dust, metal particles, carbon deposits, and soot from the oil, thereby protecting the engine. There are two types of oil filters: full-flow and bypass. The full-flow filter is connected in series between the oil pump and the main oil gallery, filtering all the lubricating oil entering the main gallery. The bypass filter, on the other hand, is connected in parallel with the main oil gallery and only filters a portion of the oil delivered by the pump.
When changing the engine oil, you basically have to replace the oil filter at the same time. I've driven long-haul trucks for twenty years and have seen several instances where drivers skipped changing the oil filter to save trouble, only for the new oil to get contaminated immediately by sludge and metal particles from the old filter. Not only does the engine noise increase, but you can scoop out half a bowl of impurities from the oil pan before even hitting 5,000 kilometers. An oil filter only costs a few dozen bucks—it's like hiring a security guard for your new oil. Especially with modern cars using full synthetic oil, it's a waste of good oil if it gets ruined by a dirty filter. My rule is simple: oil and filter must be changed together. Skipping either is doing your engine a disservice.
