Quality certification of oxygenated gasoline

A method for controlling the manufacture and certification of an oxygenated gasoline product is carried out by manufacturing a gasoline Basestock for Oxygenate Blending (BOB) at a refinery site in accordance with an empirical relationship, valid for at that site under typical manufacturing conditions, between (i) a property value of the BOB stream such as octane as determined by an on-site online process analyzer and (ii) the corresponding instantaneous value or FPAPV property value as determined by the test method mandated by the product specification for the final gasoline stream when blended with the required proportion of oxygenate. The quality of fit of this empirical relationship is calculated according to the standard deviation of the residuals of the relationship and a confidence level is fixed so that the final oxygenated gasoline formulated with the BOB will meet the required property specification when measured by the test method mandated by the specification. The final oxygenated gasoline blend is certified as having a property value conforming to the required specification based on the predicted property value for the finished gasoline.