Slick sensors lick oil trouble

Car manufacturers are turning to oil monitoring technology in the drive to improve engine efficiency

Cars and trucks could soon be equipped with advanced sensor systems that determine the quality of the engine oil and tell the driver when an oil change is necessary.

The decision on when to change the oil, which is usually based purely on a manufacturer’s recommendations, can have a big impact on vehicle efficiency. Some vehicles use computers to estimate oil quality, based on factors such as individual driving behaviour, the frequency of cold starts, fuel quality or ambient temperature. But a new generation of systems actually test the quality of the oil instead of relying upon guesswork.

For example, a sensor system that constantly monitors oil viscosity, conductivity, temperature and electrical parameters is being developed by German engineering giant Bosch. The company said that its systems will enable drivers to make ‘optimally timed oil changes’, which will both cut down on pollution and make the vehicle more economical to run.

A Bosch source added that the sensor will also provide insight into the state of the engine, making it possible to detect defects at an early stage.

However, company spokesman Richard Backhaus was tight-lipped over a rumoured 2003 launch. ‘The sensor is still in development and I can’t give you any information about the launch date,’ he said.

Meanwhile, Hitachi is working on an optical-based method that the company claimed could be adapted to all types of vehicles without the need to make any engine modifications. According to the company, the degree of oil deterioration is measured by assessing the transmission losses of near-infrared light.

At Germany’s Fraunhofer Institute for Physical Measurement Techniques Martin Jagle is heading a research project that is also bearing fruit. His team has developed a range of techniques for ‘online’ oil quality measurement, which, he suggested, overcome the inherent limitations of some of the other systems in development.

For instance, a number of projects are analysing oil quality by measuring the dielectric properties or conductivity of motor oil. The problem with this, according to Jagle, is that the accuracy of the tests can be seriously compromised by the presence of water in the oil. His team is developing a method that uses theolite crystals to determine the water content without changing the volume of the oil.

Another problem identified by Jagle is the inevitable ‘corrosion, silting and glazing’ of a sensor that is in constant contact with oil. Clearly, if a sensor becomes dirty it becomes less sensitive, and the team has developed a computational method that takes this change in sensitivity into account. ‘If the sensitivity gets lower we can detect this and use an automatic gain to compensate for the loss of signal,’ said Jagle.

He said that the solutions developed by his team are not necessarily restricted to the automotive industry. He cited the example of an expensive optical infrared measurement technique which, while potentially too expensive for use on a high-volume consumer product such as a car, would be useful on-board a ship or built into expensive industrial hardware.

A prototype ‘electric tongue’ based on infrared measurement techniques has already been developed, and Jagle said that it could be appearing on production vehicles in two years’ time.