Originally Posted By: spackard
I was sizing up a yard-sale old compressor once.
I ran it for an hour doing some outside work and it had pumped all its crankcase oil down into the tank.
I said "no, thank you!"
The compressor I'm using now did the same thing. The previous owner gave it to me for scape metal. I got it home and realized he had done two things. One, he over filled it with oil, two, he ran a screw into the vent hole on the oil fill plug, (I assume because once he over filled it, oil would flow out the little vent hole). I drained the oil, refilled it with fresh to the proper level, took the screw out of the vent hole, it works great to this day. When I first opened the drain valve on the tank, literally, at least a quart of oil came out of the tank.