Originally Posted by
mecabq
Whoa, there. Does higher octane not provide higher performance?
Not unless the engine requires the higher octane. Higher octane is there to stop uncontrolled combustion (
i.e., ones initiated by the spark plug). Higher octane = higher performance is one of the great myths. Higher octane often times does not equate higher energy content of the fuel. Higher octane because you need higher octane gasoline due to a higher (dynamic/static) compression ratio isn't a myth.
Does higher octane not cost more? Does Albuquerque not have, on average, more "low performance" autos than California, as well as a vastly lower per-capita income?
ABQ is at 1,600m (5,200') ASL. The mean altitude for NM is 1,740m (5,700') according to
Encarta. CA's is 880m (2,700') according to the same source and I would wager the bulk of Californians live within 200' of SL. Combustion chamber pressure in engines in NM are as a result is much lower than in most of CA. You'll find low octane fuels sold in California along the Sierras, and on the eastern side of the range.
I didn't know that lower octane was more appropriate at higher altitudes, but it seems from the informed posters in this thread that my assumption that less expensive, lower-octane fuel is appropriate for the New Mexico market (for reasons beyond elevation) had some merit.
Not really. But keep on digging. Colorado has similarly low octane fuels.
If you want to dig yourself out, this link may be a useful read:
http://en.wikipedia.org/wiki/Octane_rating. There's on part, which I am not too sure if I buy, that states a car running optimally with 93 octane ASL will run optimally with 91 octane at 1,000' ASL.
FWIW, my current car (or what my GF uses as her daily driver) powered by a
fuel-injected version of
this is sensitive to ambient temperature, humidity (a difference whether it's raining or just muggy), and atmospheric pressure. And the beast is computer controlled to boot. GM recommends 92 octane for the engine (or rather the successor but mine and the current are pretty identical) but I rarely put more than 89 (bulk of driving is between 0 and 150' ASL) unless it's a hot day and I intend to drive on long climbs.