When i picked up my 370z at the dealership, they've also filled my Z's tank with 89
octane gas, eventhough the minimum recommendation for octane usage is 91.
However, i don't think it damaged my engine at all, but i can ensure you that when you
fill your Z's tank with 91 octane, you can feel minor improvement compare to 89.(only if
you are extreamly sensitive person.)Personally, i put premium gas(94octane) everytime i
fill my Z's tank, and i can feel way better power than 89 octane. Occasionally, i put
Lucas octane booster with premium gas(94), which it might be raise the octane number
up to 98(approxi), and it makes me think that i've moded my Z
eventhough it's 100% stock. Just opinion
