After a certain period of usage, a new vehicle would become an old one. In regular vehicle maintenance, only for wiring system, there is still no complete maintenance technology to this day. Wires in a vehicle are just as a set of drainage system. When there are contaminant and obstructions in the latter, the drainage speed would be affected; simiarly, when the impedance in the former increases and rusty metallic vehicle housing causes bad grounding, just as what the physical theory tells us, the current would decrease (i.e. power loss), fuel consumption would increase and the emission of CO, CO2, and SO2 would increase (one of the primary causes of fog and haze).