If you've ever doubted that Mobil 1 is the world's finest engine oil, then have a look at these rocker covers after they've been put through the wringer for 200-odd hours. Ordinary oil left this thick sludge and gunk. Mobil 1 barely left a mark. That's because Mobil 1, a totally synthetic oil, is the best way to keep engine clean and why Mobil is the number one team.