I've told this before, but I was once moonlighting doing oil changes on the side. A truck driver at a lumber yard I serviced caught me the next Saturday after I serviced his truck and informed me that the oil filter had backed off on his truck. I must have had a really shocked look, because he started laughing and said he knew it wasn't my fault when it did the same thing again a few miles later. They had the truck checked and the oil pump was putting out over 150 psi.