wow...that is sad mileage...i can hit 300 w/o the light on my AT...ya...def the montana elevation should hurt it...and the 85.5 octane is lower grade than normal...so u have less dense air (which btw is why u get slower times at a hotter/higher track) and worse gas...so both the 'chemicals' are worse than ur used to...i put chemicals in quotes cuz i'm not really thinking too much rite now...which is also why this reply is kinda vague...need more explanation?