With each change, you will reduce friction and see slightly better mileage and slightly cooler running temperatures. I've heard of tranny temperature drops of over 30F.
Note that your results are typical in the change to synthetics in general, not just Royal Purple. A change to Amsoil, Redline, or even Mobil 1 would likely have produced similar results...
Congratulations on discovering Synthetics..
-P
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Guinness for strength...