I just would have assumed everyone has read or atleast been told that studies have shown that 5w-30 was overall far more superior than running ATF... i have ran 5w-30 for 2 years and don't see any signs of pump rub. When Mike switches TC's for me which will be pretty soon we'll see how much fluid i have lost to vaporization
Consider yourself among the lucky few; the pump rub problem has nothing to do with the fluid that's in the case. If the clip keeping the pump from contacting the magnesium case breaks, it will rub a hole in the case weather you have $2/qt Dex III dino or the most expensive synthetic 5W30 you can find.