What can I learn about my engine from the oil pressure gauge?
What is the oil pressure gauge?
The oil pressure gauge is the instrument on your dashboard used to report the pressure of the oil inside the car's engine. Pressure is a measure of the resistance the liquid encounters while it is flowing. As such the pressure is not by the liquid itself but by forcing it to a confined space. A good example is a river's mouth. Rivers with wide mouths tend to flow more slowly allowing silt deposits to accumulate and making them unsuitable for shipping. But rivers with a narrow mouth onto the sea are faster flowing. Forcing a liquid through a small space increases the pressure.
Inside your car's engine the oil has to travel through bore holes drilled through the engine block and into the cylinders and the crankshaft where it lubricates pistons and bearings. Oil fills the clearances between these parts. The size of these clearances affects the oil pressure. Over time wear and tear gradually increases the size of the clearances by wearing down the bearing etc causing the oil pressure to fall. This is the one cause of low oil pressure. There is not much you can do to prevent this except follow your manufacturers recommended schedule for oil changes. One of oil's tasks is to hold microscopic engine fragments in suspension. That is, hold them in the oil so they cannot get caught in a moving part and act like a scrubbing brush. However, oil can only hold so much before it becomes saturated and once it is it can actively begin to wear down the components. This is one of the reasons you'll have to change your oil. Oil also contains additives to help it clean the engine and to counteract corrosion and rusting. Other additives aid with efficiency and help the oil flow more readily when it cold and thicken up when it hot. In other words they keep the oil at a consistent viscosity or thickness. These additives get depleted over time and need replacing. That's why new motor oil is needed. Exactly how often depends on your car and your mileage. A cheap oil change is often not such a good idea in the long run I would always choose an oil which is approved by the American petroleum Institute.
Another cause of low pressure is decreasing levels of oil (you can think of this as the other side of the coin from increased clearances). The volume of oil in the engine will fall naturally over time, a long time mind you and it also depends on the number of miles you drive. You should check your oil level every few weeks, maybe monthly if you don’t drive much, and make sure it is topped up.
Other factors that affect oil pressure are the broken or worn out components such as the oil pump, the oil pressure sender unit or the gauge itself. However, when the pressure falls and the warning light comes on you should take swift action to find the cause and remedy the problem. Running an engine with low oil pressure is one of the quickest ways to ruin it. The engine seizes up and can become damaged beyond repair, so when the light comes on take action and if you’re not sure what to do get qualified advice.