I have 91 454 MAG's they have been rebuilt. From everything Ive heard these engines were built to take 87. I run 93 now because midgrade here is only 89. My question is is 87 or midgrade good for these engines? I assume performance might dip a little, and yes I know if you can afford premium your in the wrong sport. But I more of less just like to know in the event that, thats all I can find. Or the fact I just want to put 50 bucks in quick or something.