Different cars have different oil capacity levels. You can find out how much oil your car holds by consulting your owner’s manual or checking online for your make and model of car. Once you know the capacity, you can check the dipstick to see how full the oil tank is. The most accurate way to do this is to park on level ground and wait until the engine is cool before checking. Pull out the dipstick and wipe it clean with a rag. Insert it back into the tube slowly and then pull it out again to check the level of oil. If the stick shows that the oil level is below the minimum line, then you need to add more oil.