I'm needing to do crank & cam seals myself & certainly hope I don't end up with one like yours, but that appears to be the seam between your oil pan and the bottom of the block. Which, from reading isn't a terribly uncommon leak to encounter. Apparently the various o-rings get brittle over t...

On my 2001 V70, there were "about" two bolts on that side of the oil pan that the female threads went thru the engine block. These are the bolts that must get doped up with sealant or oil could leak back to the bolt head. I would imagine that leak would show on the bolt head. BTW, I doped ...