If you've been behind the wheel of a diesel truck long enough, you've probably overheard whispers and hearsay about "Black Diesel" or waste motor oil (WMO) being burned as fuel. Most of the time, you hear all of the horror stories of choked out injectors and ruined fuel lines. Someone mentions something about their engine knocking violently before inevitably stalling out and having to be towed to the shop for extensive and costly repairs. Then there's the environmentally aggressive protestors talking about black plumes of noxious smoke billowing out of the stacks like a coal refinery and something else about greenhouse gases. Many diesel drivers say it doesn't work. Some say it'll be the end of outrageous prices at the pump, but what do we really know about Black Diesel fuel?