cheep, non toxic. good for soaking.
"Solvency: Biodiesel can loosen or dissolve sediments in fuel tanks and fueling systems. Cleaning tanks prior to biodiesel use may be warranted. At a minimum, fine gauge filters should be used on fuel lines going into and out of storage tanks, as well as in the vehicle. Check these filters often during the initial phase of biodiesel use and change as needed. The solvency effect is reduced when using biodiesel blends. The solvency property of biodiesel makes it an excellent parts cleaner, but avoid contact with painted surfaces.
Material Compatibility: Biodiesel can soften or degrade natural rubber hoses and gaskets, leading to fuel leaks and spills. Most newer engines contain synthetic parts. However, older engines should be checked and any natural rubber parts replaced. Biodiesel is also not compatible with some metals and other materials. Aluminum, steel, fluorinated polyethylene, fluorinated polypropylene, and most fiberglass make acceptable storage tanks. Brass, bronze, copper, lead, tin and zinc should be avoided.
Spills: Spills of biodiesel blends should be treated as a petroleum diesel spill. Spills involving pure biodiesel require much less intensive clean-up. Consult with your local department of ecology or fire department for details.