This is like the bike forums I'm on. Starts as a thread about something unrelated, in this case belts, and turns into an octane argument...
"More octane is more better. Only the best for my baby" - can't tell you how many times I've heard that one.
I'm an 87 runner in my G. Have been for the last 80K miles (150k) total now since 2004. I don't run 87 because I "don't care", I run it because I know my car performs well with it. This has been a daily driver its entire life. I use it for everything, year round, and even tow an overweight trailer with it. 89 octane to 87 octane makes absolutely zero difference in any situation, even the most demanding ones. This is WAY more than "10k miles of research" and is also relevant directly to a G35, NOT a Nissan Sentra.
When I drove it off of the lot brand new, yeah, I filled up with 93 the first stop. After discovering that the average mileage was 20 mpg, I got quite sick of paying top dollar for the most expensive fuel at the pump only to be burning that much of it that quickly. Taking my lifelong experience with performance motorcycles into account and going to lower octanes, I started using 89 in the G. Over the course of the next few years, every time I calculated my mileage, I was at about 23 mpg with average use. Average use being highway, city, snow, and curvy country roads. I then found a gas station that offered ethanol free 87...I put it in to see what it would do. Again, car performs flawlessly in every condition. I got accustomed to the lower fuel cost. Now it's Shell, BP, Citgo....87 octane, and I'm still getting the exact same performance (arguably better when it comes to power) and the same mileage. Only time it sways is when towing a trailer, where I then average 19 mpg.
I'll let you know when my engine dies due to crappy fuel as a result of just not caring. In fact, I almost found myself pumping E85 into the tank one time because I just don't give a ****.

 

Hey guys today I changed my serpentine belt this my second time doing it and I didn’t the same thing I did the first time only this time none of my pulleys are moving and also my belt is still hella loose. I didn’t have this issue on my last G .

 

Replied to your other post.