The lifeblood of your engine. If possible, check your oil level in the morning before you start your vehicle. Pull out the dipstick and wipe clean with a lint free cloth or paper towel. Reinsert the dipstick, remove and look at the markings on the dipstick to determine your oil level. If required, add additional oil to your crankcase. If you find you are frequently adding oil, consult your service technician as to the cause. A milky color or strong gasoline odor are additional signs of trouble. Consult your owner's manual for the location of the dipstick and oil fill location.
Also check your owner's manual for the correct type, viscosity (thickness), and specification of oil to be used. Some manufacturers are very specific on motor oil.