An apparatus comprising: input fluid lines each including a flow meter for measuring a flow of a crude oil through the input fluid lines, wherein each of the input fluid lines also includes a control valve or variable-speed pump for controlling flow of the crude oil through the input fluid line; wherein each of the input fluid lines includes a spectrometer positioned upstream from a fluid mixer; a blending system including a blend header coupled to receive and combine the crude oils from the input fluid lines into a blended crude oil and a fluid mixer for mixing the individual crude oils together in the blended crude oil; and a control system operable to control flow of the crude oils through the at least some input fluid lines into the blend header thereby mixing the crude oils according to a target total boiling point curve for the blended crude oil; the control system is operable to determine total boiling point curves for the crude oils flowing through the input fluid lines using optical spectra measurements from the spectrometers; the control system is operable to calculate a blend recipe of the crude oils based on the determined total boiling point curves for the crude oils flowing through the input fluid lines and on the target total boiling point curve for the blended crude oil; the control system is operable to implement feedback control to the calculation of the blend recipe based on an actual total boiling point curve determined for the blended crude oil based on optical spectra measurements from the spectrometer; the control system is operable to control the flow of the crude oils through the at least some input fluid lines into the blend header according to the calculated blend recipe. input fluid lines each including a flow meter for measuring a flow of a crude oil through the input fluid lines, wherein each of the input fluid lines also includes a control valve or variable-speed pump for controlling flow of the crude oil through the input fluid line; wherein each of the input fluid lines includes a spectrometer positioned upstream from a fluid mixer; a blending system including a blend header coupled to receive and combine the crude oils from the input fluid lines into a blended crude oil and a fluid mixer for mixing the individual crude oils together in the blended crude oil; and a control system operable to control flow of the crude oils through the at least some input fluid lines into the blend header thereby mixing the crude oils according to a target total boiling point curve for the blended crude oil; the control system is operable to determine total boiling point curves for the crude oils flowing through the input fluid lines using optical spectra measurements from the spectrometers; the control system is operable to calculate a blend recipe of the crude oils based on the determined total boiling point curves for the crude oils flowing through the input fluid lines and on the target total boiling point curve for the blended crude oil; the control system is operable to implement feedback control to the calculation of the blend recipe based on an actual total boiling point curve determined for the blended crude oil based on optical spectra measurements from the spectrometer; the control system is operable to control the flow of the crude oils through the at least some input fluid lines into the blend header according to the calculated blend recipe.