One problem with Premium around here lately is the price.
Like Regular is $3.07 But mid level was $3.24 and Premium was $3.41
I do not know why the others are so much more.. Or is is like a 'sale'? on Regular.
But with that much increase.. i stick to Regular.
I do try to keep what is in the tank a little over Regular with a partial fillup of Premium every third partial fill.
(I usually fill it at 7 gallons or so)
Shell or Mobil gas only.