The thermostat installed on the oil cooler controls the oil temperature by allowing a part of the oil to flow through the cooler and the other directly into the fuel tank. This arrangement allows hot engine oil still below 65 ° C (150 ° F) to be mixed with cold uncirculated oil in the tank. This can increase the entire engine oil supply to operating temperature in a short period of time.

Reciprocating engine dry thin oil lubrication system-oil pressure regulating valve

The oil pressure regulating valve limits the oil pressure to a predetermined value according to the installation situation. This valve is sometimes called a safety valve, but its actual function is to regulate the oil pressure at the current pressure level. The oil pressure is high enough to keep the engine and its accessories lubricated at high speed and high power. This pressure helps maintain the oil film that fits between the crankshaft journal and the bearing. However, the pressure must not be too high, otherwise leakage and damage to the oil system may result. Oil pressure is usually adjusted by loosening the lock nut and turning the adjustment screw.

On most aircraft engines, turning the screw clockwise increases the tension of the spring, which holds the valve on its seat and increases oil pressure. Turning the adjusting screw counterclockwise reduces spring tension and pressure. Some engines use washers under springs, which are removed or added to adjust the regulating valve and pressure. Adjust the oil pressure only after the engine oil is at operating temperature and the correct viscosity has been verified. The applicable manufacturer's instructions include the exact steps for adjusting the oil pressure and factors for changing the oil pressure setting.