The continuous improvement in engine technology in order to achieve new emission norms have led to an increased amounts of petrol, diesel and soot in the engine oil during engine operation. This dilution causes a fast decrease of the oil properties. Additional, the recommended oil change intervals for automotive engines have continuously been extended over the last few decades. In many cars, this interval is calculated using a set of certain characteristic engine parameters and driving behaviour (oil temperature, engine speed, number of engine ignitions). In order to prevent engine failures as a result of abnormally aged oil, or extreme driving conditions, it is necessary to monitor the oil condition continuously. This can only be reliably realized by means of a sensor directly located in the harsh oil environment of combustion engines. The developed sensor enables the measurement of viscosity, density, permittivity and temperature of the engine oil and provides therefore relevant data for sophisticated oil condition algorithms.