Rezyd-X^® Z67 is a biodegradable, internal cleaner that maximizes solvency properties to efficiently dissolve and disperse heavy hydrocarbon sludges, asphalts, lube oils, and residues on contact. It can be used in oil or water washes to rapidly clean vessels, heat exchangers, process lines, and tanks. For water-based applications, Rezyd-X^® Z67 can be used with the proprietary ZymeFlow^® boil out method to penetrate occluded contaminants. The product can be used standalone or with other ZymeFlow^® process-compatible products. Additionally, it can be used in internal circulating systems or on-line treatments, providing application flexibility. It is VOC free, and because it is a nonpetroleum product, it has a lower toxicity and flammability than competitive petroleum and citrus- or terpene-based solutions. Emulsions made with Rezyd-X^® Z67 will break without the need for additional clean-water recovery chemicals. Wash solutions can be sent to crude storage or API separators, providing simple breakout and recovery.