Question: how do you know when you have to change your oil?
Answer: Check Engine or Oil Change Light. The most obvious alert that there's an issue with your oil will come from the car itself. ... 
Engine Noise and Knocking. ... 
Dark, Dirty Oil. ... 
Oil Smell Inside the Car. ... 
Exhaust Smoke. ... 
Excessive Mileage. ... 
Change Oil Promptly.