What octane rating should we use on a stock grand am? [Archive] - GrandAmGT.com Forum

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blondiez24gt
11-07-2009, 01:05 PM
I looked on My gas cap, and didn't see it anywhere. My brother said if my cars 9.5:1 compression ratio I should at least be running 91 octane. I've always put 87 in it. With the exception of a couple fill ups. So what should I put in it?

2000 GT Coupe
11-07-2009, 01:37 PM
87 should be fine for a stock car.

Malaclypse
11-07-2009, 03:03 PM
Regular is just fine. Anything more is a waste.

Pauljp
11-07-2009, 03:34 PM
The owners manual for my 2003 GAGT on page 5-4 recommends an octane rating of 87 or higher.
I have always used 87 because it is the cheapest.
However, about twice a year I fill up with the highest rating I can get at the pumps.
It really makes a difference.
The pickup, the idling, the purring as it's going down the road is quite noticable.
If it wasn't so expensive here in Canada for the "good" stuff, I would use it regularly.

AaronGTR
11-08-2009, 12:02 AM
9.5:1 compression is not that high. The owners manual recommends 87 octane and that is what the cars computer is programmed to use. Anything higher is a waste of money unless you have modified the engine and reprogrammed the computer to take advantage of the higher octane. Many people try using higher octane and claim it makes a difference... it doesn't. That's the "placebo effect" happening. They put something different in the tank and they want to believe it runs better so they imagine they can feel a difference. The human senses and brain aren't sensitive enough to even notice that kind of difference. Without scan data from the engine sensors and dyno testing, you can't prove it actually helps anything.

Running higher "quality" gasoline from a well known chain regularly instead of cheaper "no name" or bargain gas stations can make a difference because of the difference in the additives in the gasoline which help keep your engine clean. But that's only where you buy the gas from and has nothing to do with octane.

350rs
11-08-2009, 11:53 AM
ive always ran 87 in mine. ill run lucas through every few tanks. Does it help? who knows, but i know it sure isnt hurting.

Now the Camaro ran about 11.1 and ran terrible on 87. i bumped it up to 89 and it did a bit better, but still nothing special. So i tried 91 at quick trip, and that crap did worse than the 89. After that i ran the 93 at Mobile and ran it untill i pulled the motor. Moral of the story for me anyway is that a slightly built motor needs the extra octane, but a factory GM motor anyway only wants 87. I think even the LS7 is rated on 87.. that LS9 though.. i dont know

GA2000GTSpeed
11-08-2009, 01:02 PM
Quick Trip gas is **** compared to conoco or shell. Shell has commercials about how they have put cleaning additives in the gas. the only reason i know that conoco/Carter Energy has cleaning additives is because my dad has owned several gas stations in the past and now were down to one. it seems that my parents cars and trucks have lasted alot longer then they should have with as much as they got taken car of. one example is my dads 97 f150 went about 290,xxx miles only thing that was really ever done was the oil changes. now my dad is driving his f550 as a dd now...

GrandAmGTTT
11-08-2009, 05:24 PM
87 octane. Only need for higher octane if your using nitrous or any other major power adder.

DrFabulous
11-08-2009, 05:56 PM
87 octane for a stock Grand Am.

/thread

AleroB888
11-08-2009, 06:49 PM
87 octane for a stock Grand Am.

/thread

Except for a couple of things. The timing tables in the 3400 calibrations are pretty aggressive in the upper ranges, and in the absolute coldest weather the increased air density may warrant a slightly higher octane to be on the safe side under all conditions. Without scanning it you'd never know for sure.

In Colorado, the octane ratings for available gas are 91 premium, 87 midgrade, and 85 low octane regular (but the bastards don't charge any less for it), to account for the reduced air density. So I have no problem using 85 octane in the Summer in the stock 3400, but use 87 here in the Winter.

AaronGTR
11-08-2009, 08:39 PM
ive always ran 87 in mine. ill run lucas through every few tanks. Does it help? who knows, but i know it sure isnt hurting.

Now the Camaro ran about 11.1 and ran terrible on 87. i bumped it up to 89 and it did a bit better, but still nothing special. So i tried 91 at quick trip, and that crap did worse than the 89. After that i ran the 93 at Mobile and ran it untill i pulled the motor. Moral of the story for me anyway is that a slightly built motor needs the extra octane, but a factory GM motor anyway only wants 87. I think even the LS7 is rated on 87.. that LS9 though.. i dont know

Nope, LS7 is a 'vette motor and a 505hp v8 for a high performance version at that.... all the corvette motors are rated for 91 octane or higher, because of their compression and settings in the computer. ;) Even my parents '03 C5 with the LS1 says 91 in the owners manual.

Mike Jung
11-08-2009, 09:05 PM
Except for a couple of things. The timing tables in the 3400 calibrations are pretty aggressive in the upper ranges, and in the absolute coldest weather the increased air density may warrant a slightly higher octane to be on the safe side under all conditions. Without scanning it you'd never know for sure.

In Colorado, the octane ratings for available gas are 91 premium, 87 midgrade, and 85 low octane regular (but the bastards don't charge any less for it), to account for the reduced air density. So I have no problem using 85 octane in the Summer in the stock 3400, but use 87 here in the Winter.
I have heard people say...

In the summer due to heat might need higher octane.

& lower octane in the winter.

:confused:

This is what a guy does with his C5 LS1 Corvette.

AleroB888
11-08-2009, 09:15 PM
I have heard people say...

In the summer due to heat might need higher octane.

& lower octane in the winter.

:confused:

This is what a guy does with his C5 LS1 Corvette.

In general, for greater air density, increase octane or retard timing.....
lower air density, increase timing, decrease octane.

2000 GT Coupe
11-08-2009, 10:00 PM
I have heard people say...

In the summer due to heat might need higher octane.

& lower octane in the winter.

:confused:

This is what a guy does with his C5 LS1 Corvette.

In general, for greater air density, increase octane or retard timing.....
lower air density, increase timing, decrease octane.

So what your saying is the extreme elevation is why?

AleroB888
11-08-2009, 10:17 PM
So what your saying is the extreme elevation is why?

Right, and even though the loss of power is quite a bit, most cars get by with going down only a couple points in octane. If you have tuning capability, you can advance the timing and get a bit more power back.

Malaclypse
11-08-2009, 10:59 PM
Except for a couple of things. The timing tables in the 3400 calibrations are pretty aggressive in the upper ranges, and in the absolute coldest weather the increased air density may warrant a slightly higher octane to be on the safe side under all conditions. Without scanning it you'd never know for sure.

In Colorado, the octane ratings for available gas are 91 premium, 87 midgrade, and 85 low octane regular (but the bastards don't charge any less for it), to account for the reduced air density. So I have no problem using 85 octane in the Summer in the stock 3400, but use 87 here in the Winter.

Also consider that there are two different blends of fuel at play here. There's a summer blend for higher temperatures with a different add pack and then there's the winter blend used only during cold months.

I forgot why the EPA mandates this but cars always run better on winter blend vs summer of the same octane.

Usually if using summer blend gas and you get a cold spike, the cold-start idle of your vehicle may suffer.. and you may get some light detonation.

i_ammetal
11-08-2009, 11:42 PM
In Colorado, the octane ratings for available gas are 91 premium, 87 midgrade, and 85 low octane regular (but the bastards don't charge any less for it), to account for the reduced air density. So I have no problem using 85 octane in the Summer in the stock 3400, but use 87 here in the Winter.


Um where do you fuel? Because Ive never seen a gas station that didn't have any less of a 5 cent difference between 85 and 87.....

I wouldn't run 85 to save my ass. 87 or 91.

AleroB888
11-09-2009, 12:31 AM
Um where do you fuel? Because Ive never seen a gas station that didn't have any less of a 5 cent difference between 85 and 87.....

I wouldn't run 85 to save my ass. 87 or 91.

Usually the Phillips 66, sometimes Shell or Conoco... I didn't start driving the stock one regularly until lately. It does get occasional knock retard on scans even with 87 octane, but that's very rare. I might put a tank of 91 in to see if it disappears entirely.

350rs
11-09-2009, 07:41 PM
Nope, LS7 is a 'vette motor and a 505hp v8 for a high performance version at that.... all the corvette motors are rated for 91 octane or higher, because of their compression and settings in the computer. ;) Even my parents '03 C5 with the LS1 says 91 in the owners manual.


Really? Wow. Our 01 2500 HD ( not and ls1 i know, but based on it) is recomended to run on 87. When were pulling or hauling we use 93 though. it IS a very noticeable difference.

blondiez24gt
11-09-2009, 11:50 PM
Every now and then when my car is at idle the rpm's will jump around a little bit. Almost like a miss. That is when I am running 87. When i put 89 or higher in the car it doesn't seem to do this. Thats why my brother started telling me this. So does that mean I should use the higher octane gas? Or does that have nothing to do with the octane rating?

2000 GT Coupe
11-09-2009, 11:57 PM
Really? Wow. Our 01 2500 HD ( not and ls1 i know, but based on it) is recomended to run on 87. When were pulling or hauling we use 93 though. it IS a very noticeable difference.

The 2500 does not have the advanced timing that the vette does. I am unsure about the compression on it though.

lone_wolf025
11-10-2009, 01:00 PM
Um where do you fuel? Because Ive never seen a gas station that didn't have any less of a 5 cent difference between 85 and 87.....

I wouldn't run 85 to save my ass. 87 or 91.

Interestingly enough someone recently wrote in to the Chicago Tribune's auto guy regarding 85 octane. The response was that since places like say Denver, CO are at a higher altitude the air is so thin that all you need is 85 octane even for an engine rated at 87.