It is effective in engine fuel economy to reduce the viscous friction by applying the lubricating oil with low viscosity. The lower viscosity such as SAE0W20, however, is concerned to increase the lubricating oil consumption, LOC. Also it has become urgent to reduce the LOC because the emission of metal oxide contents from oil additives causes the pre-ignition in highly supercharged spark ignition engines or the emission of the sulfide ash, phosphorous and sulfur contents degrades the diesel particulate filter and the de-NOx catalyst. In order to clarify the mechanism of LOC with the low viscosity oils, the LOC rates were measured with a supercharged diesel engine under various operating conditions when lubricated with SAE30 or SAE10W30 test oil, and they have been compared with the rates of the evaporation from the oil-film on the cylinder wall, LOE, predicted under the analysis model for multi-component oils. The following results have been found out. (1) The change of LOC with the test oil is mostly equal to that of LOE under the same operating conditions with the gas pressure, the temperature of cylinder wall, the viscosity and the rotating speed. (2) The LOE mass flux cyclically changes with the gas pressure for each piston stroke since the evaporation depends on the saturated vapor pressure of oil species varying with the temperature. (3) The LOE increases corresponding to the content ratio of hydrocarbons smaller in molecular weight. (4) The supercharging operation has the effect to reduce the LOC of low viscosity lubricating oil because the LOE decreases as the gas pressure becomes high. (5) The devised analysis method is more useful to predict the rate of LOE for the multi-component oil and examine the influence of the oil volatility on the LOC.