1. The lubricating oil is too thin (the oil temperature is high and the brand does not meet the requirements);
2. The lubricating oil pressure is too high;
3. The gap between the piston and cylinder of the air compressor is too large;
4. The cylinder of the air compressor is out of round or worn too much;
5. Oil leakage in the cylinder of the piston air compressor: (1) The piston ring is worn too much and loses its elasticity; (2) The piston ring bites in the ring groove; (3) The gap between the piston ring groove is too large; (4) The piston ring is installed incorrectly.
6. The gap between the crankshaft bearing or connecting rod bearing of the air compressor is too large;
7. The crankcase temperature of the air compressor is too high or the ventilation is poor;
8. The oiling rod lubricated by splash lubrication is too long or the crankcase oil level is too high.