Sounds like an opportunity for you to do some research and report back to the group.
You may be better off doing 2 or 3 tanks of each in a row running it below 1/4 tank to insure you have a clean test.I was actually thinking the same thing as well. I have such an uncanny thirst for knowledge. I am still at 1/2 a tank of premium so I'll let it get abut a 1/4 of a tank, use low grade and see if there is much of a difference. i will definitely get back to the group this one.