| Trip to High Altitude [message #214623] |
Tue, 16 July 2013 15:49  |
larry.whisler
Messages: 356
Registered: August 2005
Karma:
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Senior Member |
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We returned from our first trip in the GMC to the western part of the United States.
One item that I noticed was the lower octane gasoline available at the pump, 85 octane.
I had some issues with using 87 octane in the flatlands that resulted in spark knock and possible vapor lock.
So, I am looking at this 85 octane option and thinking WTF. If
I am having problems using 87, why would anyone buy 85.
Then we traveled on toward the Tetons, and at altitude I am losing power. I am wondering what is wrong with the engine?
Then as we top over the peak, the elevation is reading 10K.
Okay, higher altitude=lower air pressure=power loss. We get back to 'flatlander' altitudes it should not be a problem.
And then it dawned on me that is why they sell the lower octane
fuel at altitude. Higher altitude = lower effective compression ratio and you can get better performance with out spark knock using the lower octane fuel.
So is this a correct assumption from a flatlander in central Indiana?
larry whisler
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