I used to work at a research centre run by a well known petroleum company where they carried out extensive research on these devices.
One of the guys there explained to me how they work:
"When you insert this device into your car cigarette lighter 12 volts DC is connected across the base plate of pre-famulated amulite surmounted by a malleable logarithmic casing in such a way that the two spurving bearings are in a direct line with the panametric fan. The hydrocoptic marzlevanes within the device, so fitted to the ambifacient lunar waneshaft that side fumbling is effectively prevented. The main winding in the device is of the normal lotus-o-delta type placed in panendermic semi-boloid slots of the stator, this enhances bhp and torque outputs, and every seventh conductor is connected by a non-reversible tremie pipe to the differential girdle spring on the "up" end of the grammeters thus reducing the amount of fuel to the injectors and contributing greatly to increased fuel savings"