Thanks for sharing your experience. It's a bit of a mixed bag; on one hand, it's good to know that running the test might not be worth the effort, thus saving time and money. On the other hand, it's a bit disappointing to think there might have been one last potential solution to the issueI wouldn't bother. I've ran a few tanks of 89 to check mileage and performance and found a negligible difference, not enough to offset the extra cost. And it certainly didn't make the engine idle any "smoother".
If I was towing heavy regularly like 8k+, I might consider 89. But for daily driving and 5k towing on the weekends (twice a year 8k), I can't tell the difference between 87 and 89.
Well, the search for the perfect fix continues! Thanks again for your input.