Jason,
If you are seeing an increase in mpg's then two things may contribute to that in your case as stated above.
the moly in the oils have reduced the friction which is very common especially when you change out gear oils.
I don't know anything about redlines fuel additive(which I assume that is what it is) but if you increase mileage from the fuel additive on a relativly good engine, then it seems to have an effect on octane in which case cannot be used as neutra 131 to purge engine oils, transmissions, gearboxes or hydraulic systems as this is not a desirable chemical property of any the listed oils i just mentioned. Now if it is designed as such then look at this, cost on neutra 131 wholesale is 1.67 per treatment, redlines is how much?
As for the seal condition aspect on the tech data sheet, As for many things that schaeffers does, they do not like to overstate benifets of anything. They are very conservative as they show the application treat rate being a whole lot less than I and many other use it. This again is on the side of caution. The actual concept of what they are stating it as purging before change over to another oil, is mainly to neutralize acids so not to put a demand on the new oil. To cover every aspect and treatment rate for every situation that this product can do would require a site like auto rx has.
I've been totally convinced from many applications that have been used, the personal testing and such, like auto rx has done with all their personal and extensive tests, that this stuff does in fact conditions seals as well as nuetralizing the acid and varnish formations among many other situations. In talking with some of the tech's they had stated the same. Is it better than auto rx, no idea. I can say that from what I have heard on here, auto rx is an excellent product, but then, so is the neutra 131. As for redline, I have no clue where it stands as I suspect their price is much higher, and not many have reported what benifets they actually have experienced with just this product. Let me also commend you for qualifying your statement about haveing done the changeover at the same time so it would have been hard to establish what in fact did help mileage.