My understanding of these devices is that they work like a capacitor in your car audio. Ie, supply that bit extra to the system when the drain is more than the system can cope with. A new car like these should not need this device and a decent battery will do the job if you are running extra toys off the stock system. Aaronng is right about the speed of the meter picking up the spikes. Try using an analogue meter as your eyes will be able to pick up the slightest movement of the needle and they do not have filtering to slow down the measurement.