The article discusses the causes of humidification of engine oil from vehicles and provides quantitative estimates of transferring of water into oil.

In exploitation of modern cars, there are cases of power unit failure due to a sharp deterioration in the properties of engine oil and loss of performance of the lubricant. The article describes the causes of failures of the engines of modern cars associated with the loss of the resource of oil in the engine and the processes occurring in the lubricant. They are increase of kinematic viscosity, decrease of Total Base Number, increase of the acid number, decrease of flash point, increase of water content, decrease of additives content, increase of wear products. Decrease in properties and motor oils lifetime was caused primarily by the deviation of the physicochemical parameters of applied motor gasoline beside regulatory petrol. The process and chemical reaction of sulfurous acid formation during engine operation are described. We have established a pattern of changes in physico-chemical parameters of motor oils in automotive gasoline sulfur compounds. Made quantification is produced by the combustion of 1 kg of gasoline sulfur acid. The low values of the loss of the alkaline number of motor oil, caused by the low sulfur content of the ecological class 5 gasoline, are a prerequisite for an increase periodicity of oil change in the operation of modern cars.

The article reflects issues related to changes in the properties of engine oil during operation. Proposals are considered for creating a methodology for assessing the residual resource of engine oil by the example of changing the kinematic viscosity. The operating conditions of cars vary greatly, which affects the change in the engine oil resource. Automotive manufacturers set the engine oil change interval in kilometers. The actual resource of the engine oil may differ significantly from that recommended by the manufacturer of the equipment and declared by the manufacturer of the oil. The article presents the factors that determine the resource of engine oil and theoretical aspects of assessing the residual resource of engine oil. To assess the residual life of the engine oil, it is proposed to select a diagnostic indicator that comprehensively evaluates the state of the operating oil, assign limit values for the diagnostic indicator, fix the values of the diagnostic indicator during daily maintenance of the car, replace the dependence by which the diagnostic indicator changes with an approximating straight line, determine the coefficients for the approximating direct based on the last and previous values of the diagnostic indicator and operating time, calculate the engine oil operating time to the limit state according to a linear relationship The results of testing and forecasting the residual resource of engine oil for a motor transport enterprise are presented. Calculations made it possible to establish that the frequency of engine oil change can be increased relative to that adopted at a motor transport company by 28.3%.

Discussed are the design features of exhaust systems of cars and the factors influencing the formation of condensation in them.