Oil condition sensors which had a two-electrode structure with an inte
rdigitated pattern and roughened electrodes were fabricated using micr
omachining techniques. With an AC sawtooth waveform voltage source app
lied to the sensor electrodes, a current dependent on the oil conditio
n can be measured and converted to a DC voltage output. The sensors we
re mounted on the dipsticks of test cars and were used for in-situ eng
ine oil degradation monitoring over 20320 km (12700 miles). The durati
on of the testing was from winter to summer, and both normal and short
distance driving were tested. Measured sensor outputs were also compa
red with oil analysis results. There was a strong correlation between
the sensor output and the condition of the oil as confirmed by the oil
analysis.