Yep, we have 85 reg, 87 mid, and 91 prem in CO. Lived here all my life, so thats what I'm use to. I know most other states start at 87.

Hopefully someone can give a good answer for this, because I'm not totally sure. It must be for altitude and the fuel/air mix ratio. But someone might have a better answer.

The outtie recommends 87, but here in Denver I switch between 85 and 87 octane. Its 10 cents different, thats $1 for 10 gallons. Like thats going to hurt my wallet.

 

Thanks tdford. There also was a 10 cent difference between 85 and 87 octane in Salt Lake City. I only used 87 and like you I figured the savings weren't worth the risk.