We ran a carbon dioxide compressor completely oil free for 500 hours at 2600 rpm, the compression ratio was 1:10 and it had an outlet pressure of 90 bars. After finishing 500 hours of operation, the piston sealing ring was as good as new.
Recently, we were assigned a test to run oil free at 250 bar. We ran it up to 450 bar and still, the seal worked flawlessly.