Why is it necessary to change vehicle oil regularly, and not just change the filter and add new oil as needed?
In: Engineering
Because the filter really only is there for when things have already gone wrong.
It can only filter actual particles. Like metal shavings or stuff that fell in while you put in oil.
But metal shavings only come by when the oil didn’t properly lubricating things.
Thing is, it’s the oil itself that breaks down when it gets heated and put under pressure. This causes parts of it to become sticky. Which prevents it from properly lubricating the engine.
That’s why the oil needs to be fully replaced.
For many chemical reactions the reaction also happens more quickly the more of the breakdown product is already there, so removing as much oil as possible also makes the new oil last longer.
That’s why synthetic motor oils are made.
They are extremely pure and specific molecules, rather than the ‘normal’ dark motor oil which was partially purified crude oil.
It’s the same with cooking oils btw: virgin olive oil can’t really be used for frying. But refined olive oil can be used.
The rifining process removes most of the non oil contaminants that would get burned during frying, allowing you to use the oil at hotter temperatures without burned taste.
But for actual industrial frying you use further chemically treated and purified oils, to allow them to reach even higher temperature without charring.
So the filter won’t do anything with the parts of the motor oil breaking down, but the oil won’t libricate well anymore.
If you engine is in good order, and you put in oil under hermetic conditions, the filter would barely be necessary
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