I'm on the Fiero West cruise and have noticed that regular gas in Wyoming and Colorado is listed as 85 octane, mid grade is 87. No 10% ethanol is listed on the pumps. Is this lower octane rating due to the high altitude? In the flat lands in Florida and up through the east coast 87 octane is regular (10% ethanol) and 89 octane (10% ethanol) is mid grade.

My 87 GT seems to run on the 85 octane. I've been doing lots of mountain driving and am still getting 28 mpg with lots of second, third and forth gear driving. Seems to be too hilly (except when going down hill) to use fifth. Gas is higher in Colorado (Colorado Springs today) and 85 octane was $3.679 at the 7-eleven next to the hotel.

We will be heading out toward Nebraska tomorrow. I'm looking forward to no hard driving on the hills and horsing the car around.

no idea but 87 is 339 here

At high altitudes 85 octane behaves like 87, so this is why we have lower ratings up here. Almost every station has ethanol......there are a few places in the state that sells 100% gas, but due to the unique pollution issues that we have in Denver oxygenated gas has been mandated now for several decades (used to use MTBE, now its ethanol).

Anyway, 85 octane is exactly the same as the 87 you get in Florida......no difference at all so don't worry about using it.