Oil Pressure

Oil needs pressure to reach the bearings, camshafts, turbocharger and chain tensioners. Pressure rises with engine speed and falls as oil gets hot and thin. The red oil can light on the dashboard means pressure has dropped below a safe minimum. It is one of the few warnings where you should stop the engine immediately.

Oil pressure rises with engine speed and falls as oil gets hot and thinner. Some engines use variable-displacement oil pumps that adjust pressure to demand. Oil pressure is not the same as oil level. An engine can show low pressure with a full sump if the pump, pickup strainer or bearings are worn, or if the oil is too thin. Conversely, a low level can cause pressure loss when oil surges away from the pickup in corners or under braking.

A gear or vane pump driven by the engine draws oil from the sump. A relief valve limits maximum pressure; many modern pumps vary output to save fuel. The pump creates flow; pressure results from the resistance of bearings and oil passages. A pressure relief valve limits the maximum.

Low level, wrong oil, a worn pump or worn bearings cause low pressure. Never keep driving with the oil pressure light on: check the level first, and have the cause found before restarting. If the red oil pressure light comes on while driving, stop safely and switch off the engine. Driving on without oil pressure can destroy the engine within minutes.