The Clean Air Act was put into place in January 1995 in the United States as part of the efforts of the Environmental Protection Agency
The increased demand for lighter, more profitable fuels has focused interest on squeezing the most out of the residual oil or "bottom of the barrel". Being sold at poor returns, the bunker fuel oil is still manufactured, but the actual trend is toward reducing its consumption.
The residual oil produced by the straight run method, nowadays, becomes the input for further processing.
In other words, the "residue" left over, after all the "goodies" are distilled, is then blended back, in most cases, with the least valuable "cutter stock" available in the refinery to meet viscosity specifications.
This new distribution of a barrel of crude oil, between distillate and residual fuels creates problems unknown in the past, but which now must be faced by today's light and heavy fuel oil consumers.
As the quality of fuel diminished, fuel-related breakdowns increased to a point where many users became alarmed.
Thus, fuel oil additives became the object of serious ongoing research in order to reduce maintenance costs and energy consumption.