Modern automotive fuel could have come from as many as 15 different sources of hydrocarbons, each affecting the final specification and overall cost. Products can be mixed by various processes, such as in-line through a multiple control system, batch mixing in tanks, and onboard mixing in marine vessels. Several factors are affecting successful blends. From tank conditions to stock conditions, checks are put in place to ensure the best results are achieved from blending. This topic will discuss challenges and factors affecting successful blends, modes of blending, blending control and optimization, mathematics of blending, blending system modules, types of blending configuration, the rundown inline open-loop diesel blender, the rundown inline open-loop kerosene blender, the rundown inline open and closed-loop gasoline blender, the inline closed-loop gasoline blending system, advanced blend control & optimization system levels, etc.