Quantitative analysis is performed on crude oils (i.e. whole oils) by injecting microliter volumes of the whole oil into the split/splitless injector of a gas chromatograph (GC). A capillary column is used to separate hydrocarbon compounds in the n-C4 to n-C42 carbon range through detection by a flame ionization detector (FID). Whole Oil Gas Chromatography allows for the evaluation of a range of hydrocarbons in a produced oil (or rock extract) as well as determining oil properties such as the presence and amount of biodegradation, thermal characteristics (e.g., using ratios of early eluting peaks to determine the extent of thermal cracking for oil generation), and source characteristics (e.g., whether the oil is derived from a marine, lacustrine, fluvial, or terrestrial depositional environment). Additionally, chromatograms produced by WOGC can be used for production allocation or reservoir continuity by comparing specific peaks and peak ratios within a chromatogram to compare and contrast multiple oil samples.