Oil is the life blood of the engine. An engine running without oil will last about aslong as a human without blood. Oil is pumped under pressure to all the moving parts of the engine by an oil pump. The oil pump is mounted at the bottom of the engine in the oilpan and is conrtccted by a gear to either the crankshaft or the camshaft. In this way, whenthe engine is turning，the oil pump is pumping. There is an oil pressure sensor near the oilpump that monitors pressure and sends this information to a warning light or a gauge onthe dashboard. When you turn the ignition key on, but before you start the car, the oillight should light, indicating that there is no oil pressure yet，but also letting you knowthat the warning system is working. As soon as you start cranking the engine to start it,the light should go out indicating that there is oil pressure.