Carrier APU question

Hey guys. ...I have had a Carrier APU on my KW since new in the summer of 2006....a/c has always lacked a lot of luster but everything else has always worked well. But recently it has developed a new problem I'm scared means a doomed ending....after starting and warming up, oil is discharging out of the engine through the blow by tube. I was wanting some opinions from some other people as to the problem or possible fix....although I'm afraid its just plain tired and wore out....what do y'all think??