Thanks for the post!

It's possible oil leaked into the cylinders and into the pump head, yes. It's unlikely you have oil in the Discharge Line to the tank, but certainly possible. Typically the valves (whether they're Reeds or Discs) would stay closed so as to prevent oil from reaching the Discharge Tube to the tank.

I would stand it up like the seller mentioned and just let it sit for a few days, but I would also remove the Discharge Tube from the pump head to confirm the presence of oil or not. If your air filter element has oil on it, and your Discharge Tube has oil in it, most likely some oil reached the tank.

If any oil reached the tank, you can purchase a solution at an industrial supply shop, auto parts store or hardware store that can rinse the tank of oil deposits (which you would then drain out of the main tank drain cock).

First, however, see if you have a soaked air filter element or if oil is in the Discharge Line.

- MTR

Hmm, if you can take a photo of it and upload it, I certainly could, but I'm sure it's just a different type of drain valve. It could be a knurled type, which has a textured piece to grip so you can turn it CCW to drain the tank.

You can see the various styles of drain valves by clicking on the below link:

www.mastertoolrepair.com/air-compressor-...n-cocks-c-25_70.html

As for the second issue, you can use a degreaser such as Purple Power, or a similar product; dilute it to about 50/50. You could spray this into the main tank inlet where your Discharge Line connect to, just remove the Check Valve first.
If you have a very small amount of oil in the line, however, I wouldn't worry about it, unless you're painting, of course. In this case, it's (obviously) important to have no oil in the line whatsoever.

- MTR