All cars need oil to run the engine. The oil used is specifically designed for use in a car engine and it varies depending on what engine you have, so always be sure to check the required oil before adding it to the sump.
You can check the oil level in your car by checking the dip stick. This is a stick that shows you the level of oil and to check it you need to remove it when the car engine has not been running (engine is cold) and the car is parked on a flat surface. Wipe the stick and then push it firmly down in to the hole. After a few seconds remove the stick and look to see where the level is. If the level is too low then add a bit of oil at a time and then repeat the checking process.
Adding too much oil can damage a car and also, so it is vital that you add it slowly and check before pouring in any more.