Here's one of the answers:

BEFORE adding oil, check the oil level to see whether the oil level is low or not, because to much oil can damage an engine too, to much oil is not as critical as to less oil but critical enough to avoid.

=> The main point
Checking the oil level is done by the dipstick, its usually a long thin flexible metal strip that sticks in the engine- block, that is that big main bulk. The dipstick has a scale on the tip that says "min" and "max". to check the oil level, the car needs to be on ground level and

Car Very Low On Oil