Just to help with the convo I will work down some terms I find speed it up in the automotive world.
Piston. Compression rings, oil ring, wrist pin, small end of the rod, big end of the rod, crank pin, crank journal, counterweights and main bearings.
That said many of these compressors use similar "off the shelf Lego parts" from China. On the Yong heng type 2 stage setups ive lost big ends on the rods running detergent motor oil in the crank case. Hydraulic oil has worked for many hours buy bypasses rings and stinks. Buying legitimate expensive breathing air dive compressor oil and monitoring temps has paid the most dividends. If you are mechanically inclined, i do recommend checking your clearances(ive crashed pistons with thermal expansion) ive cooked many "small" compressors running outside their duty cycle limits too .
There are no bearings to speak of in any compressor ive killed yet on the rods. No plain bearings even. Just aluminum on steel with an oil film. Keep in mind thermal expansion differences between aluminum and steel and film strength . Anything over 68ci should probably be filled in 2 sessions. An oil cooler mod might help too. Be aware of an air compressor that "pings" or knocks. It might be ingesting it's own oil and dieseling, exacerbating the rod wear problem and causing a dangerous hpa situation. We are in the complicated and technical end of a simple hobby, but i very much like to see guys tinkering on periphery. Why? because we can.