based on my experience,
unless you know "for sure" your tractor has never had the motor rebuilt and the new style valve stem bushing installed.
i would not add that material to the gas.
one year (many years ago) my local coop offer gas with the lead additive in the fuel for the older tractors, i bought some and started using it in my to-35,
not too long after that, my tractor head had to be rebuilt as the valve guides all seized up.
my tractor had been rebuilt before and had the new type valve guides, i did not know that using this gas would cause my tractor motor to seize.
when the mech placed the head of my tractor on the work bench, he said most of these old tractor heads will almost fall apart as they are so worn and loose, but yours had to be driven and hammered apart as each part was seized.
just a word to the wise!!!!!!