Refined products are typically the result of blending several component streams or blend stocks. Intermediate product qualities are measured and appropriate volumes are mixed into finished product storage using either batch operations or "in-line" blending methods.
While gasoline blending consumes the most time and effort, other products are blended for sale as well. Examples of other products include jet fuel, diesel fuel, fuel oil, and lubricants to name a few. Properties include flash point, aniline point, cetane number, pour point, smoke point, viscosity index and others. Many of these properties do not blend linearly, so finished properties must be predicted using sophisticated math models and experience-based algorithms. The cost associated with reprocessing or reblending off-spec product is prohibitive.