I just bought a 2002 Chevy Blazer 4x4 V6 4.3L the other day. I moved to Colorado 6 months ago where the air is thin as everyone knows. I'm used to putting 87 octane in my car. Here in Co the lowest octane isn't 87 but 85. Would I be alright with putting the 85 in my new (to me) ride?

 

I don't think it will really matter you won't see a hp increase or anything but I personally use 87 in my 84

 

Try the 85 if its cheaper. If you hear any pinging or knocking then go back up to 87, otherwise you'll be fine. General rule is to use the lowest octane that doesn't cause pinging.