Here in Colorado the lowest Octane rating for gas is 85. That is so because of our altitude there is less oxygen so you don't need 87 octane for regular gas. In fact our mid grade is 87 and high grade is 89. So, the manual for my brand new 2012 Outback says to use 87 octane. The dealer says to use 85 in the summer and 87 in the winter. Makes no sense as the air/fuel ratio is the same for winter and summer. Has anyone living in high altitude experimented with 85 octane gas?