How to diagnose whether Toyota Corolla oil circuit is dirty or not?

Toyota Corolla's method for diagnosing whether the oil circuit is dirty is as follows:

1, go to 4S shop or repair shop for cleaning;

There used to be a cleaning agent in the gas station, which can clean the oil circuit by adding it to the fuel tank.

Don't clean it if you don't find that the idle speed is unstable and you don't find that it costs more oil than before. The more you wash, the more expensive the oil is. Cleaning the throttle of the oil circuit is still quite deceptive, especially simple and expensive.