Hi guys some help needed. I am in the process of changing the engine oil.I went gungho as usual not waiting for the new Clymer book to turn up. Question is what is the drain plug underneath the water pump left hand side front. i undid it thinking that was the sump plug but to no avail.

A little oil did drop out but thats not what i was looking for. Did find the sump plug after that but would like to know what oil did come out so, if need be to replace it.
Cheers