To remain competitive, today’s refiners must employ all optimization and product control techniques available. The use of online physical property analyzers is one of the key features to reach those objectives because they measure important quality properties in the process directly. The vapor pressure is an indication of a liquid evaporation rate and relates to the tendency of volatile components to escape from the liquid. To assure safe storage and transportation of petroleum products, minimize environmental pollution and assure proper functioning of combustion engines it is important to measure the vapor pressure.