Here in Arizona, I have never seen anything lower than 87 octane.  In New Mexico, all regular I
have seen is 86 octane.  Arizona averages higher than New Mexico in elevation.  People don't
realize how mountainous Arizona is unless they have explored it a bit.  The expressways stay to
the easy ground, so driving through on I-10 or I-40 doesn't give one a realistic picture.  Well
over half the state is above 4500'.  We have several good sized towns located above 7000', and
the "occasional mountain passes" often are much higher.  Some peaks near 13000'.  Don't judge
the whole state by Phoenix, although even that valley metropolis is much higher than the
highest point in Illinois, where I grew up.

My point was that octanes are lower in New Mexico than in Arizona, even though the average
elevation in New Mexico is lower than in Arizona.  That makes me question if the difference is
strictly altitude related.  Gas sold in Phoenix is definitely different than that sold in
Flagstaff, which is 5500' higher than Phoenix.  Phoenix gas will make your car hard to start in
Flagstaff, although both say 87 octane on the pump.

Bill

----- Original Message -----
From: "John Brush" <jbrush@AROS.NET>
>
> The octane rating can be lower at higher altitudes.
>
> The reason AZ gasoline is rated 86 or 87 is because the state resides
> mostly at lower elevations, even tho an occasional mountain pass might
> exceed 7000 feet.  In CO, UT, MT, WY, and other states that pretty much
> reside above 4500 feet in most areas, the octane can be lower since nearly
> all driving is at the higher elevations.
>
> The gasoline is blended to for majority of the driving conditions.
>
> Lower octane gas is not garbage gas. Using octane that is higher than
> necessary is a waste of money.