Fuel oil and related equipment which were often designed for lighter fuels. For comparison, BS 2869 Class G heavy fuel oil behaves in similar fashion, requiring storage at , pumping at around and finalising for burning at around . Most of the facilities which historically burned No. 6 or other residual oils were industrial plants and similar facilities constructed in the early or mid 20th century, or which had switched from coal to oil fuel during the same time period. In either case, residual oil was seen as a good prospect because it was cheap and readily available. Most of these facilities
Bitumen-based fuel associated with the phenol group of surfactants. The most well known bitumen-based fuel has been developed by Intevep, the Research and Development Affiliate of Petroleos de Venezuela SA (PDVSA), in a collaboration with BP, and is branded "Orimulsion." It is an emulsion of natural bitumen mined from the Orinoco Belt and fresh water. Bitumen-based fuel is currently used as a commercial boiler fuel in power plants in Canada, Japan, Lithuania, and China. Commonly available air pollutant control technology can limit emissions from Orimulsion to levels considered Best Available Control Technology, as defined by the United States Environmental Protection Agency. Bitumen-based