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Old 11-14-2006, 12:33 AM   #1
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Default Grand prix GTP 1999 */Ced running off 87 octane mods

My friend has been running his 99 gtp off 87 octane to save money. He always ran 93 octane but he says its safe to run 87 octane if he babys it. He has custom donpipe u bend delete 3.4 inch pully intense pcm drilled 180 t-stat K+N cold air intake. Is he right is it safe to drive on 87 octane if he babys it he says max 2 lines of boost on his gauge when getting onto the freeway......
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Old 11-14-2006, 12:43 AM   #2
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I would say he'* ok, just as long as he doesn't REALLY get into boost. Mine didn't have any KR until I hit about 4psi the one time I ran 87 since I've owned the car, and even then it never went above 4*. He'* killing performance though, but that'* not what he'* after I guess.
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Old 11-14-2006, 01:37 AM   #3
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BS. He'* doing long-term damage to the pistons at the very least. If he can't afford the premium fuel, he can't afford the car.

I gaurantee he has KR. KR means the PCM HAS ALREADY SEEN THE KNOCK AFTER IT HAPPENED.

Premium Unleaded Fuel Only means exactly that for a reason.
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Old 11-14-2006, 02:18 AM   #4
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Will is absolutely right. All the "authorities" on L67s that I know tell me that a stock L67 is borderline able to run 87. Any kind of mods, and 91 or better is absolutely required. Your friend is going to pop a piston running that crap.
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Old 11-14-2006, 02:21 AM   #5
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If he'* stock pullied he'll be fine on 87. Any other pulley nope! The PCM has "Good fuel" and bad fuel" settings, after a while of driving on 87 the car will just become a turd.

GM builds these cars to withstand stupidity for the most part. A stock L67 will take almost anything. If its modded-play nice.
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Old 11-14-2006, 02:41 AM   #6
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I know of 1 person that had to run 87 octane fuel, but that was because there was nothing else available to use. That would be the ONLY situation I'd understand using anything less than premium fuel.

Running premium in these */C cars is a decision you make when you get the car. He has the wrong car if he thinks he can do otherwise.
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Old 11-14-2006, 04:46 AM   #7
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I run 91 in my L36 with 5 ounces of MMO added to 12 gallons.
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Old 11-14-2006, 08:21 AM   #8
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Premium fuel is interpreted a little differently depending where you live, although it never means less than 91. 87 is a pretty drastic drop in octane, predetonation is a given.

Bad things are happening, it'* a matter of time before they start to show up.
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Old 11-14-2006, 11:22 AM   #9
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Quote:
Originally Posted by willwren
BS. He'* doing long-term damage to the pistons at the very least. If he can't afford the premium fuel, he can't afford the car.

I gaurantee he has KR. KR means the PCM HAS ALREADY SEEN THE KNOCK AFTER IT HAPPENED.

Premium Unleaded Fuel Only means exactly that for a reason.
Bill is so right on the money!! Tell your friend to not be so damn cheap! It calls for premium fuel for a reason. Your friend should have taken that into consideration when he bought the car if that was going to be an issue. Jeff & I have informed a few people we've seen at the pumps and they said they were told it was okay and didn't realize what it could do to their cars. Those other people steering him wrong ain't gonna have to live with the end results.
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Old 11-14-2006, 11:25 AM   #10
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Quote:
Originally Posted by SSE14U24ME
Quote:
Originally Posted by willwren
BS. He'* doing long-term damage to the pistons at the very least. If he can't afford the premium fuel, he can't afford the car.

I gaurantee he has KR. KR means the PCM HAS ALREADY SEEN THE KNOCK AFTER IT HAPPENED.

Premium Unleaded Fuel Only means exactly that for a reason.
Those other people steering him wrong ain't gonna have to live with the end results.
OR help pay for them either
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