$5.47, available at Walmart
SuperClean Degreaser has a multitude of cleaning uses, so it comes in handy for many of your car detailing needs. I wouldn't recommend using it at full strength on your paint, but it works wonders cleaning built-up oil, grime, or dirt on your engine bay, under-body, or exhaust pipes. When diluted, it does a great job at cleaning carpets, floor mats, and chrome pieces as well.