Low sulfur fuel is desired by many industries because it is cleaner for the environment and optimal for engines due to containing few particulates (soot) and few sulfur oxides. To conform to specific environmental regulations, fuel oil has a maximum sulfur content level which is typically set as a weight percent. Low sulfur content in fuel can also increase the efficiency of catalytic converters, prevent corrosion of metal parts, and reduce the blackening of production facilities.
Residual fuel oil is the heaviest among a range of different fuel oil grades. Residual fuel oil is primarily used in simple furnaces like power plants and industrial boilers, and also used as the primary fuel source on ocean liners. Specific standards are set for residual fuel oil by governments to maintain levels of performance and to meet environmental regulations.