http://www.jim-van-blaricum.net/blog
Oils refined with the clay-solvent process contain a fair amount of paraffin and wax. These molecules cause several problems in an engine: they sometimes fall out of solution, leading to buildups in your engine that must be cleaned out somehow. Also, as these molecules get hot they thin out quite a bit, much more than mineral oil, so they make the oil’s high temperature performance rather poor. Finally, at low temperatures the waxes and paraffins thicken the oil so much that you really couldn’t call it a lubricant. If you’re curious about this, buy a cheap quart of straight 30wt oil and put it in your refrigerator or freezer over night. You’ll be amazed at how thick it becomes. More than half the motor oil sold in N.America in 2004 is made from base oils refined with the clay- solvent process (I like to call it the Kitty-litter and Kerosene refining method), but I don’t think this is the type of oil you want to put into an engine you love. These oils are roughly 85% good stuff (oil) and 15% bad stuff (paraffin and wax). To put this in perspective, think of taking a gallon of really excellent oil, and melting a 12″ dinner candle into it. Jim E Van Blaricum