An oil pressure sensor is an instrument used in your car’s engine to measure the pressure of the oil as it flows around the engine from the oil sump through the filter, into the engine and back again to the sump. It is not used, as is often thought, to measure the volume of oil in the engine. When any liquid flows through or over a surface it pressure is a function of the amount of liquid and the volume of space it has to fill. Pour a liquid through narrow funnel and the pressure increases when the water exits the funnel. Pour the liquid into a bucket and there is no pressure as such because there is no restriction placed on the liquid. The same is true in your car’s engine and that is why pressure is directly affected by the volume of oil so a reduction in the volume will lead to a reduction in the pressure.
An oil pump helps to create this pressure. The pump draws oil up from the sump and passes it through a filter to remove unwanted particles. After the filter the pressure sensor measures the flow and sends a signal to the car dashboard if the pressure is too low. The oil accumulates in an area called the galley before being forced through tiny boreholes and then out through nozzles to be sprayed onto the engine. Here it provides lubrication cleaning and cooling services before falling through the engine and accumulating again in the sump with the whole process begins again.
Often when the oil pressure falls the simple fix is to add more oil to the car. It’s a good idea not to wait for the warning light to come on but instead to proactively check the level. If you have to top up make sure you use the best motor oil you can find. The best oil is usually the one recommended by your car manufacturer or one which has been approved by the API in America or SAE in Europe.