I'm only on my second tank and I put 89 octane in it because some guy who worked as a fuel delivery driver told me that there wasn't really any difference in the plus vs. premium, but some difference in 87 standard. I don't think I have noticed anything yet, but the car's pcm would take the timming down to compensate. You don't notice it as much in a GM LT1 350 V8 as much as you will in the Nissan 3.7 V6. I'm still experimenting.
