by Douglas Samuelson

Created on: April 27, 2008

Checking the oil in your car is the easiest, most important, and most neglected preventative maintenance on your car.

Oil not only provides lubrication for the internal parts of your engine and transmission, it acts as a coolant and contains additives that help to keep the engine and transmission clean and to prevent seals and gaskets from becoming brittle.

There is a misconception regarding the oil pressure warning light and/or oil pressure gauge Most people think that this light or gauge is an indicator of the amount of oil in the engine crankcase. The light is designed to come on when engine oil pressure is lower than the normal operating pressure for that particular engine. Oil pressure is the amount of pressure (measured in pounds per square inch) generated by the engine oil pump, to supply oil to the internal engine parts. Granted, if the engine oil level is so low that the oil pump cannot suck oil from the oil pan, the light will come on, but by this time, severe engine damage may have already occurred. The oil pressure gauge serves the same purpose, but it is a better indicator since it can detect a gradual change in oil pressure. It is normal for engine oil pressure to decrease somewhat as an engine wears, but at no time should an engine be operated when the oil pressure is below the recommended operating pressure.

Most engines can be operated without immediate damage when the oil level is one or even two quarts low, but they should not be run for an extended period of time. When the oil level is low, momentary starvation of the oil pump can occur when the vehicle is in a turn which will allow the oil in the oil pan to "slosh" away from the oil pump pick-up screen. This momentary lack of oil will not always be detected by the warning light or gauge.

The best time to check engine oil level is when the engine is cold. If the level is checked on a warm engine immediately after it is shut off, there can still be a small amount of oil in the upper engine that has not drained back into the oil pan. Over-filling an engine with oil can sometimes be as damaging as a low level. If the crankcase is too full, the oil can be "churned" by the rotating crankshaft counter-weights, causing the oil to be aerated.

Some people will say "My car does not use oil. Why should I check it so often"? My answer to this is "S__t" happens". An oil filter can leak if not properly tightened after an oil change. An oil pressure sending unit can develop a leak. A valve cover gasket or

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