Oil Leak When Shutting Engine Off?

[athenshome]

I've got a 1997 GMC Sierra 5.7L that we bought from a friend. I noticed that when you shut the engine off, a small puddle of oil will spit out. It does not continually drop oil or drop while the engine is on, but only drops this small puddle when you shut off the engine. The puddle size is really not very large, but definitely large enough to get your attention when you move the truck.

 

We took it to my mechanic and he replaced the upper and lower oil cooler lines, but the oil is still dropping. I asked him to look at it again to make sure the lines were seated correctly and he said they were.

 

Can anyone lend some advise as to where to look next for a solution? I know this maybe a broad question without looking at it, but this is the first time I've had this issue on any of my GM cars. Thanks in advance!