It used to be good for cars that sat outside a lot in the winter and didn't get driven much. With E10, you don't need it unless somehow you got mild water contamination from a gasoline station that doesn't sell much gas.
Probably not needed anymore. I went though a Catalytic class that work sent to me a few years ago. The instructor said the Isopropyl dry gas keeps converters clean. So I look for 4 packs of it at WM when they put them on clearance. I will use a bottle every 4 to 5 months.
Does it do anything? I have no idea. I always put Shell V-power in my Regal.
Although Dry Gas is really not needed for vehicles during the winter, I still use quite a bit of the liquid.
I run some alcohol stoves for camping, hunting, fishing and the dry gas is the best to use. I scored on almost 50 bottles of the, "yellow bottle", on clearance at Sears, a couple of years back, on a visit to Florida.
For 40 cents a bottle I cleared the shelf! Still the best fuel for an alcohol stove to cook a pot of coffee or soup in the outdoors in the cold or rainy weather.