My 2007 Tacoma has a lot of engine/oil black gunk around the bottom of the engine bay (below the battery and that area). I'm talking about solid black. Could that be caused by a leaky oil pan gasket? What else possibly could be the reason?
It very well could be the oil pan gasket, but this could be caused from a leaky anything on the engine. Look for where the highest point of where you see the gunk and start looking from that level. You should also be seeing some amount of gunk on the engine as well. If you really want to find it, do a thorough cleaning of the entire engine bay, then start looking for where the leak originates from.