In the last few years, dispersants have been widely used as the primary response measure for marine oil spills around the world. Until recently, the U.S. Environmental Protection Agency (EPA) protocol for testing the effectiveness of dispersants in the laboratory was the Swirling Flask Test (SFT), which was found to give widely varying results in the hands of different testing laboratories. As a result, EPA developed an improved laboratory dispersant testing protocol, called the Baffled Flask Test (BFT). This protocol uses two crude oils (South Louisiana and Prudhoe Bay) at one temperature, 20DGC. Recent interest in the dispersability of heavy refined oils such as IFO 180 and IFO 380 at different temperatures has emerged. SFT tests were conducted at the University of Cincinnati on these two oils with Corexit 9500 as the dispersant. The test gave very poor results, dispersant effectiveness being less than 10 percent at a dispersant-to-oil ratio (DOR) of 1:10, mixing speed of 200 rpm, and a temperature of 16-1 oC. Under the same conditions the Baffled Flask Test (BFT) showed good dispersant effectiveness on both fuel oils. It was deemed that further tests with SFT would be fruitless. Further evaluations using the BFT to determine the effectiveness of three commercially available dispersants, Corexit 9500 (C9500), Super Dispersant 25 (SD25), and Agma on IFO 180 and IFO 380 oils were conducted. This report describes experiments to study the effect of different variables such as DOR, mixing speed, and temperature on dispersant effectiveness of these heavy oil products.