A small engine-oil-deterioration detection sensor was developed and installed at the tip of a dipstick gage. The sensor part was manufactured using printed circuit board (PCB) manufacturing technology. A set of sensor covers was installed in order to protect the sensor and realize good signal stability. The small engine-oil-deterioration detection sensor system comprised a dual sensor having etched copper electrodes coated with gold and ceramic, a flexible PCB (FPCB) acting as electric wire, and a dummy PCB with only a lock connector. The sensor can easily be installed by insertion through the guide tube of a dipstick gage. Thus, a driver can easily handle it without further installation equipment. The sensor can determine the level of deterioration in the engine oil by estimating the corresponding dielectric constant of the engine oil.