1.1 This specification covers four grades of fuel oil made in whole or in part with hydrocarbon-based used or reprocessed lubricating oil or functional fluids, such as preservative and hydraulic fluids. The four grades of fuel are intended for use in various types of fuel-oil-burning industrial equipment under various climatic and operating conditions. These fuels are not intended for use in residential heaters, small commercial boilers, combustion engines, or marine applications, 1.1.1 Grades RFO4, RFO5L, RFO5H, and RFO6 are used lubricating oil blends, with or without distillate or residual fuel oil, or both, of increasing viscosity and are intended for use in industrial burners equipped to handle these types of recycled fuels. NOTE 1: For information on the significance of the terminology and test methods used in this specification, see Appendix X1. 1.2 This specification is for use in contracts for the purchase of fuel oils derived from used lubricating oil and for the guidance of consumers of such fuels. This specification does not address the frequency with which any particular test must be run. 1.3 Nothing in this specification shall preclude observance of national or local regulations, which can be more restrictive. In some jurisdictions, used oil is considered a hazardous waste and fuels from used oil are required to meet certain criteria before use as a fuel.