Where's the oil coming from?

[IFallsRon]

The last few time's I've changed the oil filter on my 88 Silverado 4.3, I've noticed that most of that area is covered in oil. It doesn't seem to make a difference what kind of filter and I always hand-tighten. I've been cleaning off the area and the mating surface with some carb spray and a rag. The surface doesn't have any nicks.

[tidalcock]

Try cleaning and drying the area completely one evening and leave the truck alone overnight. Check it again the next morning for any oil trails that might give you a clue to its source. If you find nothing, drive the truck for a day and check again at the end of the day.

Good luck