You should heat the distilled water to about 120° before adding any electrolyte. Then add the electrolyte to the heated water while monitoring the amp draw. Once the desired maximum amp draw is reached stop adding the electrolyte. Doing it this way will ensure that the amp draw does not get our of hand.
The reason the kia is not sustaining the good MPG is because the cars computer learned and has made adjustments to the air to fuel ratio. You can correct this by tricking the cars computer or loading a new program into the cars computer. You can also disconnect the batter for a half hour and allow the computer to reset the computer.
2006 Ram, 5.9 cummins HO. 4 cell design, 1.5 LPM@30amp, 24.3 MPG