An apparatus and a method for automatic determination of cloud point temperature and pour point temperature of a petroleum fraction. The apparatus is comprised of a receptacle for holding a sample of the petroleum fraction, a light source, a light detector, heaters, coolers and a proximity sensor combined with a motion indicator to determine cloud and pour point temperature. The apparatus has thermocouples to determine the temperature of samples within the container as the sample is heated and cooled. Measurements of light refraction are used to determine cloud point temperature. Detection of the freezing in place of a motion indicator is used to determine pour point temperature. The apparatus is particularly useful for determining the cloud point and pour point temperatures of middle distillate petroleum fuels and the pour point temperature of dark oils and for determining the amount of pour point depressant needed to achieve desired cloud and pour point temperatures in a fuel.
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