Abstract: Disclosed herein is a method of assaying a crude oil, the method includes measuring at least two selected properties of the crude oil with one or more laboratory-independent devices using at least two different techniques wherein each technique is predictive of each respective property, transmitting the measured properties to a processor capable of reconstructing a determinative assay of the crude oil from the measured properties, and reconstructing a determinative assay of the crude oil from the measured properties. The disclosed method provides real-time information of a refinery feedstock such that, for example, a trader negotiating the sale of the product has accurate assay information on which to determine whether to sell or purchase the product.