Third cylinder ring blow by. Basically it's a super cheap compressor and not expected to last.
Heck cant you be gentle on the folks and say it with some degree of sympathy like:
"Im sorry but all things come to an end at some point in life it's just that some things don't live as long as others. But look on the bright side its was still a super cheap compressor and was not expected to last that long. A compressor that burns twice as bright burns half as long and yours have burnt so very brightly.
But it had a good innings it tried hard and did its best it was never expected to last it's in a better place.
You see that's much better. We cant have two of us playing the bad cop it's not fair or inclusive. Besides it's the 4th stage ring blow-by not the third. And my apologise for the blatant rip from Tyrell: Blade Runner