Can the car run on mid grade (89) Octane ok? - Pontiac GTO Forum
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post #1 of 11 (permalink) Old 11-24-2004, 02:51 PM Thread Starter
 
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Can the car run on mid grade (89) Octane ok?

The owners manual says minimum recomended octane is 91.
The manual also says that the car will have problems with anything LESS THAN 87.
In SC and all southeastern states, we only have 87, 89, and 93.


Am I hurting anything if I run the mid grade here at 89 octane (yes, I'm being cheap
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post #2 of 11 (permalink) Old 11-24-2004, 04:09 PM
 
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I have used one full tank of mid grade. It didnt seem to make a differance to me, but the computer in the car may think otherwise.
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post #3 of 11 (permalink) Old 11-24-2004, 08:34 PM
 
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I have used 89 for several weeks, no problems. I haven't had the courage to try 87 yet.
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post #4 of 11 (permalink) Old 11-24-2004, 08:49 PM
 
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I think the LS1 has a anti-knock sensor so you can use the 87-octane, the engine just retards the timing to compensate and you get less power. I've run 87 octane in my Z28 several times. The LS1 is such a great engine, I just feel I am depriving it if I don't feed it high-octane all the time.
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post #5 of 11 (permalink) Old 11-24-2004, 09:14 PM
 
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It will run, but you will see a major decline in
acceleration & performance.
This is a high compression (for 2004 that is) engine & it will run
much better on 91 or as we have on the east coast 93 octane.
How much are you really saving anyway maybe $2 per tankfull
Also if you decide to do any mods, especially having the car tuned
or using the predator performance tuner you will need to use at least 91 since
their performance tunes change the engine timing for the use of
premium fuels only
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post #6 of 11 (permalink) Old 11-24-2004, 10:43 PM
 
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Ours has run almost totally on 87 since it was new. No pinging or any other adverse effects. The several times that I ran 93 in it, I noticed no difference in performance. Maybe on the drag strip it would show, but it didn't show in everyday driving.
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post #7 of 11 (permalink) Old 11-27-2004, 01:17 PM
 
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All Grades

I've used all grades from BP & Speedway. In normal driving on highway & around town I've seen no difference in performance.

I can't say I drive the car hard though.

Fuel economy and the acceleration on the street appear same between grades.

How much performance can you tell on the street. When I get on the GTO it is usually up to or beyond the speed limit by 3rd gear anyway.
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post #8 of 11 (permalink) Old 11-28-2004, 09:57 AM
 
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Here in Iowa we have 89 with 10% ethanal. Any thoughts on using it? It's cheaper than the 87.
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post #9 of 11 (permalink) Old 11-28-2004, 05:06 PM Thread Starter
 
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I think I recall the owners manual specifically saying not to use fuels with ethanol or other alcohols.
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post #10 of 11 (permalink) Old 12-04-2004, 06:41 AM
 
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I've tried 87, 89, and 93 with multiple fill-ups of each. I found that they all "feel" the same, I didn't notice any performance differences between them. What I did find was that with 87, I got some knocking when initially starting the car, but not after that. I didn't particularly care for that so I won't be using 87 at all anymore. What is interesting, though, is the mileage differences. I consistently get in the 17's using 93, 18's using 87...and 19's for 89. I have no idea why, but it seems 89 is the mpg sweet spot, at least for mine (it's an A4).
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