Is there a reason why you cannot use the factory specified 87 RON/MON fuels? Are they not available in your locality?
At high altitudes (1 mile/1.6 km above sea level) less octane is needed because the air is less dense (standard air pressure is 12.1 psi versus 14.7 psi at sea level), net result is as if the engine had a lower compression ratio. So regular gas is 85 RON/MON. 87 is premium. I run 87 when I'm (rarely) in the lowlands.
Last edited by Spider; 08-28-2011 at 12:12 PM.