Abstract: On-line sensors sense the kinematic viscosity, the infrared absorption, at a predetermined wavelength, the ultraviolet absorption of a predetermined wavelength, and the sulfur content of crude oil and corresponding signals are provided to a computer circuit. The computer circuit solves the equation:M%BP={--C.sub.1 +C.sub.2 [ln(IRxC.sub.3)]+C.sub.4 [lnUV]--C.sub.5 S--C.sub.6 [ln(IRxC.sub.3)](lnUV)+C.sub.7 [ln(IRxC.sub.3)]S}lnKVwhere M%BP is a particular percent boiling point property of crude oil, IR is the infrared absorption of the crude oil, S is the sulfur content of the crude oil, KV is the kinematic viscosity of the crude oil, UV is the ultraviolet absorption of the crude oil and C.sub.1 through C.sub.7 are constants.

Abstract: On-line sensors sense the kinematic viscosity, the infrared absorption, at a predetermined wavelength, and the sulfur content of crude oil and corresponding signals are provided to a computer circuit. The computer circuit solves the equation M%BP={C.sub.1 --C.sub.2 [1n(IRxC.sub.3)]--C.sub.4 S+C.sub.5 [1n(IRxC.sub.3)]S }1nKV, where M%BP is a particular percent boiling point property of crude oil, IR is the infrared absorption of the crude oil, S is the sulfur content of the crude oil, KV is the kinematic viscosity of the crude oil, and C.sub.1 through C.sub.5 are constants.