Check your car manual to determine which type of oil is recommended for your car. Synthetic oils may be a bit pricier, but are often recommended to aid in engine function. If you have been using synthetic oil but want to switch to natural, purchase a natural oil. If you have been using natural oil and would like to switch to synthetic, choose a synthetic oil.
Park your car on a flat surface in a space where you have plenty of room to move around the car. Turn the engine off and let it cool for at least an hour. After an hour, open the hood of the car.
Remove the oil dipstick. This is a long piece of metal attached to a small handle. It will be located near the center or left side of the engine. If you cannot find the dipstick, check your car manual for a diagram.
Wipe the oil off the dipstick with a rag. Then re-insert the dipstick back into the oil. Remove it once again to check how much oil is in the tank. The oil on the dipstick should reach the "full" line. If the oil is below the full line, the dipstick should tell you how much oil you need in order to reach the full line.
Add the appropriate amount of your new variety of oil to the oil tank. Re-insert the dipstick to find out if you have filled the oil tank. If the oil has not yet reached the "full" line, continue adding the new oil until the tank is full. When the oil has reached the full line, the mixing is complete.