What are the major parts of the engine oil system?
The oil pump consists of a drive gear, rotated directly by the crankshaft, and a driven gear that is spun by the inner gear. Together, as the teeth mesh, oil is pressurized and sent to the oil filter where it is pumped through and into a passageway where it can enter the crankshaft. As the crankshaft rotates, it helps draw oil into itself and draws oil to the main bearings. The pressurized oil flows into the bearings where the crankshaft rises on a film of oil so it does not make direct contact with the bearings. The oil bleeds out of the bearings and drains back into the oil sump where excess oil is held so that it may be picked back up into the oil pump. There are passages that deliver oil to the camshafts and also pressurized oil is delivered to a spool valve that blocks oil flow to the camshaft sprocket on a variable valve timing equipped engine. The spool valve or oil control valve can allow oil to pass into different passages where it would then flow into one of two oil cavities in the camshaft where the oil can pressurize the camshaft gear/sprocket often referred to as a VVT actuator or gear on either side so that the angle of the gear is advanced or retarded in reference to the camshaft position. The pressure inside is held and has no where to go so that the VVT gear can be held in a range of positions until a change in valve timing is commanded by the ECM, and pressure is bled down when it is allowed. The cylinder walls and camshafts often have their own oil squirters to lubricate and control heat. The bottom piston ring referred to as the oil ring holds oil around the piston and the ring(s) above it scrapes the oil off of the cylinder wall so that the engine does not burn oil. The drain holes in the cylinder head and engine block allow oil to fall back down directly to the oil sump. On newer models, the oil pump has a pressure control valve and can raise or lower pressure on demand. Also on newer models the VVT camshaft gears are replaced with electric motors that can hold valves open enough to eliminate pumping losses while coasting, improving efficiency and gas mileage.
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A reservoir of oil is provided by the sump which is the lower part of the lubrication system.After the oil has been forced into the required area it falls back down into the sump ready to be picked up again and circulated on and on.The oil pump forces engine oil through the engine passages and distributes the oil to components in differing quantities. The oil in the drilled passageways is under pressure so when the holes line up the oil is forced through them. There are also pressure valves that open to make sure that oil doesn't go above a certain psi that could damage internal components. The performance of a lubrication system is mainly controlled by the overall efficiency of oil pump along with its inlet and outlet components. If this pump becomes defective, the engine stops receiving oil and may suffer engine failure. An auxiliary pump can help prevent this headache. The lubrication system also requires filters along with the pump to keep the oil clean. Periodic replenishment of oil is done at every service to cater to any losses due to vaporisation or leakages.The oil cleans the engine by picking up dirt and depositing it in the screens or filter, or by keeping that dirt in suspension until the oil is changed!!! :)