The timing of lubricating oil changes for passenger vehicles are based on set time or mileage intervals specified by their manufacturers. A few vehicle manufacturers use more sophisticated methods such as logging the engine speed and temperature and calculating the oil change intervals from this data. Neither technique tells the vehicle user anything about the true state of the oil.
A novel form of viscosity sensor based on a vibrating piezoceramic element has been developed. Based on the output from such a device, a more accurate determination of the oil change interval can be made and abnormal conditions (such as the leakage of fuels into the lubricating oil) can be detected.
This paper gives a brief description of the device itself and shows results from prototype samples.