From: "B.Greg V"
It is indeed legal since it is not a tire "softener" per se. It essentially puts the moisture back into the tire. It restores the tire to its original durometer, not making it softer than it originally was. It just makes them last longer by allowing them to remain competitive throughout their tread life.
From: Rocky E.
I first discovered FVTT more than 15 years ago. Once upon a time I had a brand new set of tires for my Divisional, and finished .2 behind a very good driver that today has six National Championships under his belt. A year later, same tires, now turned to stone, I was six seconds off the pace. About this time I discovered FVTT and took a chance that was 5% the cost of a new set of tires. It brought them back. Another year later, still on the SAME set of tires, I won my Divisional. Two events later the tires went to cord.
I had never taken a set of tires to cord before. Always sold them off with about half the tread left when they were rock hard. Now I never do. I always run mine until there's nothing left. I treat them regularly with FVTT.