Oil residue on air dryer

[brijn]

Hi,


While crawling around under the bus for the first time, I found my air dryer:


Sorry, rotated 90dgr. There is no oil residue on other things around it. Is there any reason to find oil on there? The blow out on the bottom is clean.


I'll clean it up and see if it comes back. But curious if there is anything to be concerned about.


Tx
Bas