A system for evaluating a crude oil sample and calculating an indicative property of a naphtha or gas oil fraction of the crude oil sample without first distilling said naptha or gas oil fraction, the system comprising: a Fourier transform infrared spectrophotometer; a non-volatile memory device that stores calculation modules and data, the data including density of the crude oil sample and Fourier transform infrared spectroscopy data indicative of transmittance values at predetermined increments between a predetermined range for the crude oil sample, the data derived from an analysis of the crude oil by the Fourier transform infrared spectrophotometer; a processor coupled to the non-volatile memory; a first calculation module that retrieves the Fourier transform infrared spectroscopy data from the non-volatile memory, that calculates a crude oil Fourier transform infrared spectroscopy index value of the fraction from the transmittance values of the spectroscopy data, and that transfers the calculated Fourier transform infrared spectroscopy index into the non-volatile memory; and a second calculation module that calculates the indicative property for the fraction of the crude oil from a two-variable polynomial equation with predetermined constant coefficients developed using linear regression techniques, and that stores the indicative property into the non-volatile memory device; wherein the two variables of the two-variable polynomial equation are the Fourier transform infrared spectroscopy index and the density of the crude oil sample, wherein the Fourier transform infrared spectroscopy index (FTIRI) of a desired crude is given by the following equation: FTIRI desired crude = maxtrans desired crude - maxtrans lowest value, and wherein FTIRI desired crude is the Fourier transform infrared spectroscopy index of the desired crude oil, maxtrans desired crude is the maximum transmission of the desired crude oil and maxtrans lowest value is the minimum value of the maximum transmittances of a number of crude oils under investigation. a Fourier transform infrared spectrophotometer; a non-volatile memory device that stores calculation modules and data, the data including density of the crude oil sample and Fourier transform infrared spectroscopy data indicative of transmittance values at predetermined increments between a predetermined range for the crude oil sample, the data derived from an analysis of the crude oil by the Fourier transform infrared spectrophotometer; a processor coupled to the non-volatile memory; a first calculation module that retrieves the Fourier transform infrared spectroscopy data from the non-volatile memory, that calculates a crude oil Fourier transform infrared spectroscopy index value of the fraction from the transmittance values of the spectroscopy data, and that transfers the calculated Fourier transform infrared spectroscopy index into the non-volatile memory; and a second calculation module that calculates the indicative property for the fraction of the crude oil from a two-variable polynomial equation with predetermined constant coefficients developed using linear regression techniques, and that stores the indicative property into the non-volatile memory device; wherein the two variables of the two-variable polynomial equation are the Fourier transform infrared spectroscopy index and the density of the crude oil sample, wherein the Fourier transform infrared spectroscopy index (FTIRI) of a desired crude is given by the following equation: FTIRI desired crude = maxtrans desired crude - maxtrans lowest value, and wherein FTIRI desired crude is the Fourier transform infrared spectroscopy index of the desired crude oil, maxtrans desired crude is the maximum transmission of the desired crude oil and maxtrans lowest value is the minimum value of the maximum transmittances of a number of crude oils under investigation.