I'm pretty sure my '07 "requires" 91/premium per the manual & stickers. But, since I'm a bit over sea level, 87 has been working fine. If I lived at no elevation, I'd probably use 89 or 91. The CPU will adjust the timing so that the engine doesn't knock, and I doubt one would notice a difference running 87 vs 91 at sea level. At least I haven't when I've been that low.