A car’s oil pump is needed to make sure the engine oil reaches all moving parts that require lubrication during an engine’s operation.
Most modern engines have a wet sump (a reservoir of oil beneath the crank shaft), which is where the oil pump is installed.
Oil is supplied to the pump via the oil filter, which catches any stray particles, such as swarf, which would damage the pump.
From the pump, the oil travels around the engine via channels, grooves and holes to lubricate the cam bearings and crankshaft, while the crankshaft itself will send oil up to the base of the pistons and lubricate the piston rings.
Oil is also needed at the top of the engine, to lubricate the lifters, rocker arms and valve stems and springs.
Oil pumps usually last the lifetime of the car. In older cars the most common type is the gear type oil pump, which uses two sets of gears to pump the oil out.
Nowadays most modern cars use the eccentric rotor oil pump, which has internal and external lobes, driven by the camshaft.
Oil pumps have a pressure sensor near their outlets, which activates a dashboard warning light if it drops below a certain threshold.
If it illuminates pull over and switch off the engine as soon as possible, because engine parts won’t be getting the lubrication they need and could seize.
Engine oil pressure is higher when an engine is started from cold, because the oil is thicker. Once it has warmed up the pressure drops.
A pressure relief valve is there to get rid of excess pressure should it become a problem
It’s very important to change your car’s oil according to your car maker’s recommended intervals, together with the oil filter.
Haynes recommends once a year or 10,000 miles, but some models need more regular changes.