Is this because the narrow band O2 sensors is detecting the additive and telling it that the gas is running to lean, So in return I'm using more gas?
I have yet to find a fuel additive which will do diddly for fuel economy. Unless, as in your case they displace gasoline resulting in messing up the feedback system
What do you want from us? You put junk in your truck. So?
Pull it off the spindle, and reposition correctly
