i reckon it works on old car but not on the new ones though - grounding.
as for the voltage stab, it's a good to have for those ICE enthusiasts, but not a MUST. Other than that, it does work on automatic cars as the gear change become much smoother and well like someone said, u dun even realize that the car is started cuz it's so quiet. for that kinda price, dun expect to get a gain in any horsey.
