So I've got an oil leak somewhere on the right side of the engine. . .

last summer I posted about seeing a lot of smoke behind the truck going up a grade. It's a hard thing to reproduce, but finally was able to do so with my wife driving the truck and me in another car behind. The smoke is not coming out the tail pipe lol. Last night I was able to see that it was coming from the cat area on the right side. This morning I got under there and I can see oily residue all along the heat shield above the cat. Going forward I see oily residue around this sensor. It's just ahead of the starter, one wire coming out, and just above the level of the oil pan mating surface. It appears that there is oil possibly coming through the body of the sensor, as I see oil on the wire. So what is this sensor?

Whatever is leaking, it's enough that it put oil droplets on my windshield following the truck about 100 feet behind. I also see oil on the bellhousing, but possibly not enough to indicate a rear main seal leak. There are no drips on the ground nor have there ever been. motor currently has 185.5k miles on it.

That sensor does not go all the way into the block. It is a knock sensor and it threads into the block anout half way then the hole is closed and it detects detonation and knocks through the engine block itself so no oil through there

Haha dammit. Sounds like I'll be looking further toward the front of the motor then.

that or the oil pan seal is leaking. if it was further upfront you would likely see stains up there as well. get the engine degreased real well and reinspect it again.