Why is it necessary to change vehicle oil regularly, and not just change the filter and add new oil as needed?

Question

Why is it necessary to change vehicle oil regularly, and not just change the filter and add new oil as needed?

In: Engineering

Answer 1

I mean, I’ve had an engine that burned and leaked oil BAD. Like basically replacing all of the oil every 2 months or so. On that vehicle I just changed the filter every 4 or 5 months because the engine was changing its oil on its own.

But for properly running engines they really don’t burn much oil so adding new oil as needed doesn’t really work, at least not enough to have good fresh oil when its needed.