An oil pressure gauge measures the pressure of oil flow through an engine and displays it on a convenient gauge dial for the user to monitor.
If the oil flow drops off, an internal combustion engine can be ruined in a matter of seconds due to the high rate of rotation and the contact of metal on metal. Some vehicles, for example use what is called an idiot light to warn the user that the oil pressure has dropped below a set rate. Unfortunately, the engine may be ruined because the oil pressure was too low for an extended point before the light was triggered. With an oil pressure gauge, one can see the actual rate and can stop to investigate if the pressure is dropping off.
Oil pressure gauges are one of the most common add-on instruments for performance vehicles, along with a charging system monitor and water temperature for the cooling system.