RigMaster Power says that it’s safe to use biodiesel fuel in its auxiliary power unit equipped with the Perkins 2-cylinder engine. However, that comes with a caution to use no more than a 5% blend (B5) of biodiesel, and that fuel must comply with ASTM standards. Biodiesel mixtures above 5% could result in filter blockage, the company warns. Rigmaster’s APU runs off the truck’s fuel tanks. Biodiesel is a clean-burning alternative diesel fuel, made from soybeans, agricultural oils and fats or recycled restaurant grease. The U.S. Environmental Protection Agency officially classifies biodiesel as a fuel additive that can be blended with petroleum diesel to be used in diesel engines with little or no modification.