To provide information on the distribution of oil deposition inside the pipe conducting oil mist used for lubricating purposes and to show resulting variations of oil/air ratio. The model of an industrial pipeline has been assembled ranging more than 100 m away from the oil mist source, equipped with devices collecting oil deposited inside the pipes. Other tests were performed in stands constructed as parts of pipes coiled in helical form. Long time experiments with continuous oil mist flow enabled to achieve calculable results. The quantitative results obtained in experimental investigation on the reduction of oil/air ratio in an oil mist header system show that considerable differences of the oil/air ratio may be observed in a typical long pipeline. Possible consequences of oil deficiency on lubrication of remote mechanisms are presented in the case study. Results of tests are shown in diagrams and tables. These results may be useful for correction of design calculations procedures. Tests have been made on the basis of one kind of the oil atomized in typical condition and conveyed with steady flow through the piping of rather simple geometry. However, there are other factors affecting oil droplets deposition and the most influencing are probably: the flow velocity/pipe diameter factor, oil atomization characteristics and the geometry of the oil mist piping. The research has shown dramatic decrease of oil content in the long distance systems that may result in poor lubrication of remote mechanisms or over lubrication of those located close to the oil mist generator. More than half the total oil deposition is collected by the initial 30 m of the pipeline. It is proposed to make correction in the calculation of oil mist demand for mechanisms in remote locations to avoid results of insufficient lubrication that may reduce mechanisms lifetime. Presented tests have been carried in the scale and flow parameters very close to those applied in industry. Thus, the results are reliable and could be very useful both for designers and the practitioners of centralized oil mist systems.