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One of the most important handicaps when using the oil analysis technique for predictive maintenance, is the processing of the results. The oil analysis technique allows obtaining relevant information about the state of the lubricant, the engine and other auxiliary elements. However, it is necessary, to process this information and to define the references with which the numerical results obtained must be compared. In the system considered the different analyses performed on the oil sample have been divided into three different types: oil properties, oil contaminants and engine wear elements. Consequently, each type of result is evaluated in a different way. Finally, the evaluation process of the different analyses allows the system to qualify each analysis with a numerical value which will be used in an expert system.

This paper presents a diagnostic technique for the detection of some faults in internal combustion engines based on analysis of rolling block oscillations produced in engines mounted on elastics supports (used to minimize the transmission of vibrations). Therefore, the block (assumed as a rigid body) has some freedom of movement which becomes manifest through oscillations with respect to an axis approximately parallel to the crank-shaft. These oscillations can give information about possible failures, specially those which are related to the differences in the behavior among the cylinders. With these considerations, a method has been developed that allows an approximate determination of the instantaneous crankshaft torque through the measurement of rolling block oscillations. These oscillations can be calculated from the measurement of tangential acceleration in a block point which allows the calculation of block angular acceleration.