My car's owner's manual states that 91 octane fuel is recommended (not required). So I was curious this last time I filled up and put in 87 octane with 2.5 oz of TC-W3. I was expecting a good amount of power loss and knocking, because that's what people on the Maxima board say they experience using regular in a VQ35. But so far I can't feel a noticeable loss of power and I don't think it is any louder. I don't know what knocking sounds like though. So far I have 55 miles on the tank and gas mileage seems to be close to when I use premium, but I won't know for sure until the next fill up. The car has a knock sensor so I guess it's doing its job. Am I just not sensitive enough to these things or is my car working fine on 87?