Two personal experiences with MMO:
2004 Ford Explorer. I kept getting a CEL for (I'm paraphrasing, I don't remember the exact wording) fuel level too high. Regardless of how much fuel was in the tank, the gauge would randomly peg overfull.
I believe it was an Explorer forum I read of a couple folks using MMO to fix the problem. Sure enough. I put 8 oz in before I fill-up every other tank; fill up at 1/2 tank. Took care of the problem, sending unit reads correctly now all the time.
I tried 1 oz in a gallon of 40:1 for a 25-year-old Mcculloch string trimmer. It run awful and finally quit altogether. I drained the gas and put fresh in w/o MMO, and it was back to running great again.