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Discussion Starter · #1 ·
So, a lot of people on FB in the Ascent Groups have been asking what octane they should use. It's 87 octane (or higher), everywhere on the planet, regardless of climate, and regardless of altitude.

I explain why here:

4992
 

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Discussion Starter · #3 ·
In CO, regular gas is 95 octane and regular beer is Coors. Draw you're own conclusions.
85 and Coors? Lol!!! Watered down all the way. 😁 :ROFLMAO:
 

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85 and Coors? Lol!!! Watered down all the way. 😁 :ROFLMAO:
did you know? Coors and champion spark plugs:
"The company struck a deal with Champion Spark plug in 1940 when Champion decided to focus on making spark plugs. Coors Porcelain acquired their chemical and scientific porcelain business, including Champion's labware line and processes for isostatic forming, spray drying, and ceramic insulators. "
 

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In CO, regular gas is 95 octane and regular beer is Coors. Draw you're own conclusions.
Dang...I'd need at least Fat Tire... :) :D
 
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I'm too lazy to go look yet... Does octane change with altitude? When we were traveling last year (pre-covid) I kept to the 87 or above number even when we were in areas of higher elevation, and regular gas was below 87. Does the 87 from lower altitude stay 87 when moving up? Or should I be buying higher octane if I am planning to go to altitude to cover changes?
 

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Discussion Starter · #9 ·
I'm too lazy to go look yet... Does octane change with altitude? When we were traveling last year (pre-covid) I kept to the 87 or above number even when we were in areas of higher elevation, and regular gas was below 87. Does the 87 from lower altitude stay 87 when moving up? Or should I be buying higher octane if I am planning to go to altitude to cover changes?
Always 87 octane, no more than 15% ethanol, no matter where, how high, or what you're doing with a stock tune.
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I'm too lazy to go look yet... Does octane change with altitude? When we were traveling last year (pre-covid) I kept to the 87 or above number even when we were in areas of higher elevation, and regular gas was below 87. Does the 87 from lower altitude stay 87 when moving up? Or should I be buying higher octane if I am planning to go to altitude to cover changes?
A non turbo engine can use lower octane at higher altitudes and be fine (which is why you see 85 as "regular" in Colorado).

But a turbo engine (like the Ascent) compresses the air, so it largely ignores altitude changes which is why you MUST always use 87 in the Ascent.

You also don't need higher octane in the Ascent unless you add a tune like the Cobb Accessport that will take advantage of the extra octane regardless if you are at sea level or 14,000 ft up.
 

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I'm not quite sure my point was understood - if I buy 87 octane gas at sea level, and then on the same tank of gas travel to altitude, is it still 87 octane? I.e., does octane number depend on altitude? Or would I need for example 89 sea level octane to have 87 octane when transported to altitude?
 

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Discussion Starter · #12 ·
I'm not quite sure my point was understood - if I buy 87 octane gas at sea level, and then on the same tank of gas travel to altitude, is it still 87 octane? I.e., does octane number depend on altitude? Or would I need for example 89 sea level octane to have 87 octane when transported to altitude?
It is always 87 octane, at any elevation, for any use. Anything above that is optional. Anything below that should never be used.

Octane ratings are not based on altitudes.
 

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Thank y'all; that mirrors what I thought I understood through searching - that older carbureted engines could handle lower octane at attitude, in that there was less air, the mixture would then be more fuel rich relatively and less prone to detonation/pinging. So gas could be sold with lower octane at altitude with no real problems. But now, we need 87 or better, no matter the altitude being drive.
 

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Naturally aspirated engines can get by with lower octane at altitude because the maximum pressure reached in the cylinder during the compression stroke is less. Higher compression pressure requires higher octane. Turbocharged engines can increase and actively control inlet pressure so are not limited by ambient pressure (within reason).

Modern naturally aspirated engines with closed loop mixture control (all current engines that meet emissions reg) automaticlly adjust the mixture for high elevations and so are not running rich, though they can still use lower octane gas due to the lower pressure.
 
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