I live in Colorado at about 5000 ft, so our cheapest fuel is 85 octane. I have used it for a while in my 06 V6 without any problems. But recently I looked at the manual and it said I should not use 85 and should fill it with at least 87. Do you think they just mean not to use 85 at lower elevations??
In theory 85 octane at altitude is roughly equal to 87 at sea level, which is why it’s offered where you are. If you never drive to a lower altitude then in theory it should be ok. In practice though I don’t know if I’d feel comfortable with it. The octane rating for a car is meant to be a minimum number. And for whatever reason my car seems to run slightly better on 89 that 87 even though it's spec'd for 87 (but I’m only 200 ft. above sea level). Here’s a link:
I'd be careful with 85 even if you're not pinging. It can still cause some eventual damage. If you MUST run 85, then I suggest you de-tune for it. Since you seem more concerned with saving money, the loss in performance (if any) shouldn't matter. Otherwise, spend the few extra cents for peace of mind and put in the appropriate octane.
the octane with the tune changes the detonation of the fuel, which could cause problems. why take chances for a few cents. i would think you should run the 87.
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goina hundred in a 55, and i dont know why..
some things were just meant to be..
05 V6 auto, torch red, basic,:cool: a few mods
06 V6 stick, vista, premium (g/f`s car)
85 octane question 
