Old Faithful

I have a 150 cfm roatary. It blew all the oil back out of the air intake and shut down. I havent tried to replace the oil an restart it. Would like to find out what may have caused it. Thinking the pressure switch may have malfunction but it didn't exceed the tank safety pop off. This thing is 34 yrs old but still does the job. Really need this thing, my 100cfm not enough to handle the whole shop. Elbert Campbell, Statesville, NC