ALTHOUGH MOST PETROLEUM PRODUCTS can be utilized as fuels, the term "fuel oil," if used without qualification, may be interpreted differently in various countries. For example, in Europe, fuel oil generally is associated with the black, viscous, residual material that remains as the result of refinery distillation of crude oil, either alone or in a blend with lighter components, and it is used for steam generation for large slow-speed diesel engine operation and industrial heating and processing. In the United States, the term "fuel oil" is applied to both residual and middle distillate type products, such as domestic heating oil, kerosine, and burner fuel oils.