WHY YOU SHOULD CHECK THE OIL YOURSELF

Why you should check the oil yourself? The problem with driving into a service station and allowing the attendant to check your oil is that the dipstick always reads a little low because so much of the oil is still inside the hot engine rather than in the oil pan. By adding more oil until it reaches the “Full” level on the stick while the engine is still hot, the attendant may overfill the engine and damage it. 

For this reason, always wait at least ten minutes after you shut off the engine before allowing anyone to check the dipstick. If you don’t feel like sitting around at a gas station, the best time to check your oil is first thing in the morning, when the vehicle has been sitting all night and the engine is cold.

Source: autorepairfordummies