The average quality of crude oil being processed in refineries is becoming higher in sulfur and heavier [120]; that is, a greater content of heavy ends or residuum. With the growing demand for transportation fuels, the refiner is faced with mounting pressure to make better use of the “bottom of the barrel”—the residuum that formerly went into low-quality products such as No. 6 and bunker fuel oils. Diminishing worldwide demand for these latter fuels is exacerbating the need to use this material to produce other products, especially lighter fuels [121]. Moreover, as environmental restrictions increasingly limit sulfur and aromatics in transportation and burner fuel oils, refiners are facing new challenges to economically producing a marketable slate of products from heavier, higher sulfur feedstocks. These challenges generally require new or expanded processing and treatment technology at the refinery. This, in turn, translates into the need for new analytical test methods in the laboratory to adequately evaluate feedstocks and monitor product quality (Table 1).