I just talked to my dad. He had the oil changed in his Cadillac yesterday at the same franchise (not the same store though) that I did. This morning he noticed a LARGE oil leak under the oil pan. He was smarter than I am though because instead of messing around he took it directly to the Cadillac dealer. They told him that not only had they left out the washer on the drain plug but THE PLUG WAS NOT EVEN FROM A GENERAL MOTORS CAR!
He ended up having to have the oil changed (again) and had to have the oil pan replaced because the tech at the instant oil change place stripped the darn thing out trying to get the wrong plug to fit.
How could anyone possibly make that stupid a mistake?