All MAZDA 323 engines are equipped with a so-called circulation lubrication system. The oil pump draws oil from the oil pan and delivers it to the main oil filter. There is a pressure reducing valve on the pressure side of the oil pump. If the oil pressure is too high, the valve opens and some of the oil may drain into the oil pan. Through the middle of the filter cartridge, the purified oil enters the main oil line. There is an oil pressure sensor that signals the driver about insufficient oil pressure. If the oil filter is clogged, the bypass valve supplies oil directly to the main oil line, bypassing the filter. A diesel engine, in addition to the main one, may also have a bypass oil filter. In this case, part of the oil flow branches off and passes through the filter. From there, the purified oil flows back into the oil pan.
Channels for lubricating the crankshaft bearings depart from the main oil line. Through oblique holes in the crankshaft, oil is supplied to the connecting rod bearings. At the same time, oil flows through the ascending oil lines to the cylinder head and lubricates the camshaft bearings, rocker arms and valve stem ends. Some MAZDA 323 models are additionally equipped with an oil cooler for better heat dissipation. In this case, the oil after the filter flows through the water-cooled oil cooler.