A warning light on the dashboard of the car and low levels of oil on a dipstick reading are two of the most common ways of checking if an engine is low on oil. A warning light indicates there is a problem, while a dipstick is a guide that shows whether or not the oil is filled to the correct level. Strange engine noises as well as the color of the oil in the engine are two other signs of low oil.
If there is no warning light on the dashboard, or if further checks are required, the first step is to check the dipstick. It is important not to get a false reading from a dipstick though. It should be removed from its holder and wiped with a cloth before being put back in to get the reading. There are usually two lines on the dipstick: an upper level and a lower level. The oil level should be between those two lines.
If the oil on the dipstick is a deep black color, this can also indicate problems with the oil level. Finally, noise sometimes indicates low levels of oil. Oil lubricates the moving parts of an engine, but it also reduces the noise produced by metal components working together. If there is not enough oil, the engine may be noisier when it is running.