A refinery faces tough market competition. Hence, it must be automated. For competitive functioning, blending models must be updated for specific time intervals. In this context, important blend model parameters are ethyl equation constants, NIR model parameters, DuPont coefficients, and indexed constants. Blend model customization is required for every 90 blends or after 90 days. Blend control applications use model bias. They are dynamic as well as time-dependent. They also depend on blend grade. This topic will discuss the need for blend model updates, a review of blend model parameters, updates for DuPont coefficients, ethyl equations and diesel qualities models, system architecture to regression model parameters, ethyl equation for octane, ethyl equation for distillation points, the flashpoint for diesel, etc.