Air Filter Check and Water Drain Plug >> found Engine Oil

[BusyWeb]

Hello, GZ Masters.
I have a question about Air Filter Water Draining.
Last weekend, as general learning purpose, I had checked Air Filter.
Service Manual says that un-plug water drain plug and remove water from it.
I did, strangely, and found Engine Oil instead of water from it.
Not much, just couple of tea spoon amount...
However, air filter was in greate shape and clean, no dust at all.
Is this a normal ?
Or, do I need to check some where else places if I got engine oil instead of water out from the hose?
Or, am I missing something else, like air filter type ???

Thanks in advance for the tips...