Yes, I accidentally put 87 in once and putting a load on the engine at low RPMs (read: anything more than 1/4 throttle at low RPMs) caused TERRIBLE knocking. With 91, I only occasionally get slight knocking under load with 1/2 throttle or more I'd say.

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MARC/CROSVS | UCLA Bruin, B.A. Econ, Aug 2004 | J.D., Thomas Jefferson School of Law, May 2008 -- MEMBER: California State Bar, December 4, 2008

2005 BMW 645 Cabrio | Black Sapphire Metallic, Ti trim | 6AT | fully loaded sans HUD

2000 Ford Mustang V6 | laser red on tan | 5-spd | track-prepped