An abbreviation for saturates, aromatics, resins, and asphaltenes, which are the four solubility classes of hydrocarbon fractions of crude oil. The saturates are generally iso- and cyclo-paraffins whereas aromatics, resins, and asphaltenes form a continuum of molecules with increasing molecular weight, aromaticity, and heteroatom contents. Asphaltenes can also contain metals such as nickel and vanadium. A SARA analysis is a method used for the characterization of heavy oils based on fractionation.