Pennzoil used to run several commercials like that. I especially remember one with Packers QB Brett Favre. They ran a variety of motor oils (the fine print at the bottom of the screen indicated the test conditions) and drop the pan. The one using Pennzoil came out clean, while the other ones were black and gooey. Then Favre asked, "So what will I do with these other oils?" at which point he dipped his finger into a black-sludged pan and smeared it under his eye like athletic eye black. Of course there was a disclaimer of, "Do not use motor oil residue as eye black."