This chapter discusses basic properties and specs of crude oil and refinery products and their significance in industrial functions. These properties embody boiling level, density, viscosity, molecular sort composition (paraffin, naphthene, aromatic content material), elemental evaluation, sulfur and metallic contents, freezing level, carbon residue, pour point, flash point, cloud point, vapor strain, flammability range, wax and asphaltene contents, octane number, cetane number, aniline point, and carbonto- hydrogen ratio. Not all of these properties are necessary for every product and often additional specs are required for every gasoline, together with, liquefied petroleum gasoline, gasoline, diesel, jet gasoline, and gas oil. For heavy merchandise, properties corresponding to viscosity, sulfur content material, wax and asphaltene contents, and carbon residues are measured and reported. Specifications recommended for various fuels together with biodiesels by commonplace organizations and manufacturers within the United States and Europe are also presented. Crude assay information include density, viscosity, sulfur content material, acidity, steel content, and salt and water contents, and selected assays are introduced for several crude oils all over the world. Minimum laboratory information needed by designers and operators for crude oil refining and numerous products are also discussed.