well, I've used the 87, and there has been no knocking under load or otherwise, at all, so I don't think it's an issue. I think my mileage may have suffered 5%, but I can't tell because most of that was the cold winter. I am averaging now 24.5 on my daily commute. sometimes I put 91, sometimes 87, depending on the spread and what I feel like. Let's put it this way-I've had no adverse affects from 87, so I won't hesitate to use it. Mu pld Cad Eldorado was the same way, it said to use prem, but I had no knocking on that one either, even when I pushed it hard. I've been comfortable though putting 91 in most of the time.

 

I'm from BC and I use the 92 mid-grade Husky, which is six cents a litre cheaper than the competitors' 91 "premium". I used to use Shell V-Power, but found that this premium gas generated a smell from the exhaust (similar to what happened when I used V-Power on my old Prelude, which ended up having major engine trouble). As a result, I don't scrimp on the gas, and I don't fill up with V-Power.