93 Octane on a 91 tune - Pontiac G8 Forum: G8 Forums - G8Board.com
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post #1 of 7 (permalink) Old 02-12-2010, 09:41 AM Thread Starter
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93 Octane on a 91 tune

I have a 91 Vararam Cortex Tune installed on my G8 GT (because most all gas stations where I live carry 91 as their highest grade)

But sometimes when I fill up in different towns, I pull in and notice they don't have 91 as an option.

They have 87 89 93

So I put in 93. Would that have a negative impact of performance for that tank of gas? What about fuel mileage? Remember the car is "tuned" for 91.

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post #2 of 7 (permalink) Old 02-12-2010, 09:55 AM
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Very little problem at all.

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post #3 of 7 (permalink) Old 02-12-2010, 09:56 AM
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No negative impact. However, if you have a 93 tune, I would hesitate using 91 gas often. As for gas mileage, I don't think you will see any difference - good or bad.

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post #4 of 7 (permalink) Old 02-12-2010, 10:39 AM Thread Starter
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cool thanks.

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post #5 of 7 (permalink) Old 02-12-2010, 12:08 PM
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On tunes, you shouldnt downgrade octane, but you can upgrade without issues.

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post #6 of 7 (permalink) Old 02-13-2010, 11:04 AM Thread Starter
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Quote:
Originally Posted by mi04se1 View Post
On tunes, you shouldnt downgrade octane, but you can upgrade without issues.
good to know.

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post #7 of 7 (permalink) Old 02-13-2010, 04:34 PM
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Quote:
Originally Posted by jrc1122 View Post
I have a 91 Vararam Cortex Tune installed on my G8 GT (because most all gas stations where I live carry 91 as their highest grade)

But sometimes when I fill up in different towns, I pull in and notice they don't have 91 as an option.

They have 87 89 93

So I put in 93. Would that have a negative impact of performance for that tank of gas? What about fuel mileage? Remember the car is "tuned" for 91.
As other mentioned, no negative impact on using 93 octane on a 91 tune, but you would have problems the other way around.
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