This first post here lists the info you are asking about, in terms of the
'why':
TC-W3 Testing on the LS-1 Forums
The good thing is that this LS1 forum has a long track record of approx. 2% to 5% MPG increase. And that was basically side effect for this particular LS1 forum. But, that gets into the margin of error for home testing for sure.
The good thing that this EM thread is that we use an off the self product that is inexpensive and is not being hawked by a member with only sales motives. So it is cheap and easy to test for us, or at least try it instead of the other more expensive things like Lucas UCL or MMO that we may be purchasing every so often anyway.
I am using my unsuspecting wife's van as test vehicle, to discount any mods or hypermiling. It burns oil, and maybe it will help seal it better.
I hope to see an MPG increase, but if I see her van running nice and not burning as much oil, that is also a positive for me. So I plan on being as scientific as I can.
But, this is why it is an open discussion, vs. a very specific test; so people can try it out for our own reasons, and report experiences, anecdotal, scientific, or otherwise, and others can make of it what they want from our experiences
Hope that helps explain this thread. No one has skin in this game, like some other threads, pushing expensive fuel additives. So it seems to encourage more honest dialouge I have found.
Thanks for your interest!