I don't drive my Fiesta in winter. So i never saw a point to additional rust inhibitors.
Well, that decision ended up burning me.
My 2016 Fiesta ST started showing evidence of rust creeping out of the door , hatch and hood panels at the seam edges. Fords warranty does not apply to corrosion in body seams.
So now i have a situation where a car that is not winter driven with rust bubbling out of the edges of body panels under the edge where the outer panel wraps over the panel frame.
Something was changed in the paint preparation process. My 2011 fiesta, also not winter driven, is absolutely spotless in this regard.
I probably should have popped for a good paraffin based treatment. Every closure panel on my 2016 is steadily rotting away at the seams.