91 vs 93 octane...difference?

**knoll5150** · 05-23-2009, 04:29 PM

Think I may have answered my own question but just was curious if anyone out there have had similar scenerios in their LS1's. I know these engines need premium gas to run well, but I had been going to a "discount" gas place that sold 91 octane as their top of the line gas. Never thought about it, but I had noticed my car losing power around 2500 rpms, usually just before shifting. I had the plugs, fuel filter changed, and even the fuel system cleaned last year, yet i would still notice a bit of hesitation from time to time. No engine lights came on, care idled, and cruised smoothly...just noticed this power loss. Not major, but noticeable. Since switching to 93 octane, it seems to be disapearing, no mechanic can tell me what it is w/out a light coming on, or charging me to start tearing the engine apart. Car has abut 75,000 miles on it. Has anyone else noticed a difference between 91 and 93 octane...and is it worth going to a place that sells even higher octane gas? I've heard also higher mileage cars, sometimes need the highest octane gas to run smoothly (even non-performance engines). Just wondering if anyone else has their 2 cents on this. Appreciate any thoughts from you guys!

**levityinc3** · 05-23-2009, 04:50 PM

I'm almost 100% positive that 92 octane is what GM said the engine SHOULD run on. Around here there's only 87, 89, and 93. I try to mix, but usually just end up switching 89 and 93. That is all I can contribute.

Here ya go.

"Recommended Fuel"

http://www.gmperformanceparts.com/En...4322&engCat=ls

**Firebirdjones** · 05-23-2009, 04:58 PM

I lived in Ohio and ran 94 octance exclusively in both 4th gens and the older classic cars as well.
Just had good luck with it. I have since moved to Arizona where 91 is the only thing available. I have 2 classic cars that are now complaining alot.
The 4th gens seem to be okay for the most part. I have found they seem to be a little more sensative at wide open throttle to a little knock.
The timing curve that I had dialed into my 02 was perfect in Ohio with 94,,,but now gets 1-2 degrees of knock here in Arizona on 91.
Been currently dialing in the timing curve on my wifes LS1 and it's being a bit of a pain as well,,,pulling some timing and what not. I'm getting a handle on it though. This 91 gas is definately showing me signs of not being that great compared to the pump gas I was used to in Ohio.

I tend to stay away from the cheapo gas stations, also where you can get discounts like sams and cosco isn't the best.
I've had to drain entire tanks of gas and toss it out from places like that.

To go a little more in depth on the LS1,,,it has 2 timing tables it can run off of. And using a low grade of fuel will cause some knock, and the engine will keep reducing timing until the problem is solved,,,so you do lose a little bit of performance,,,and mileage as a result.

Pump gas will continue to deteriorate. Mixing more chemicals and lowering octane even more is probably in our future. I know for a fact that Ohio (Sunoco) isn't going to carry 94 for too much longer. They have already switched most stations to 93. It's sad but something to keep in mind.

**allbaugh_04** · 05-23-2009, 05:19 PM

I'm running on my last tank of 93 and it's tuned for it. None of the gas stations have 93 this year...I'm SOL

**levityinc3** · 05-23-2009, 05:24 PM

Originally Posted by allbaugh_04

I'm running on my last tank of 93 and it's tuned for it. None of the gas stations have 93 this year...I'm SOL

This is sort of on topic... When it is tuned for 93 octane, do they program the ECU to make the plugs spark hotter? And is that all?

**allbaugh_04** · 05-23-2009, 05:29 PM

I wish i would of asked my tuner actually, i'll see what he says. I plan on a cam swap later this summer so i'll have him clear that up for me when i get that done

**levityinc3** · 05-23-2009, 05:33 PM

Originally Posted by allbaugh_04

I wish i would of asked my tuner actually, i'll see what he says. I plan on a cam swap later this summer so i'll have him clear that up for me when i get that done

Let me know please, when you find out. Unless someone answers before that.

**allbaugh_04** · 05-23-2009, 05:34 PM

Eh, I don't plan on doing that till Junish

**levityinc3** · 05-23-2009, 05:35 PM

Originally Posted by allbaugh_04

Eh, I don't plan on doing that till Junish

No rush. Don't have any money for an oil change, let alone a tune haha.

**allbaugh_04** · 05-23-2009, 05:37 PM

Rebuilding the 4L60E, converter, cam swap, then an oil change in my future

:... too much $$$ spent

**levityinc3** · 05-23-2009, 05:41 PM

Originally Posted by allbaugh_04

Rebuilding the 4L60E, converter, cam swap, then an oil change in my future

:... too much $$$ spent

I am envious. I need to find a dirty old rich woman to seduce.

**allbaugh_04** · 05-23-2009, 05:45 PM

Join the military, you'll be at work so much you won't have time to spend your money.

People think us military guys make dope money, not the case

thats just the way it is.

At work till 11 fyi

**Y2KPewterSS** · 05-23-2009, 05:48 PM

Originally Posted by levityinc3

I'm almost 100% positive that 92 octane is what GM said the engine SHOULD run on. Around here there's only 87, 89, and 93. I try to mix, but usually just end up switching 89 and 93. That is all I can contribute.

Here ya go.

"Recommended Fuel"

http://www.gmperformanceparts.com/En...4322&engCat=ls

Owners manual states 91 octane or higher is recommended.

**levityinc3** · 05-23-2009, 07:23 PM

Originally Posted by allbaugh_04

Join the military, you'll be at work so much you won't have time to spend your money.

People think us military guys make dope money, not the case

thats just the way it is.

At work till 11 fyi

Funny you say that. I'm joining the Army, hopefully as EOD.

Originally Posted by Y2KPewterSS

Owners manual states 91 octane or higher is recommended.

Haha. My car didn't come with an owner's manual. I heard a long time ago (can't remember where) that running a higher than recommended octane wears piston rings. Any truth to this?

**allbaugh_04** · 05-23-2009, 07:33 PM

my god, good luck man

**Mr. Luos** · 05-23-2009, 08:26 PM

Were you able to hear any audible pinging?

If not...it is probably something stupid, like a dirty MAF more than the fuel.
Unless that 'cheap' 91 octane was part water.

**knoll5150** · 05-24-2009, 04:53 AM

No pinging that I can tell. I kind of thought bad o2 sensor too. Unfortunately, no mechanic can tell me if it's bad until the thing goes out. Again, I don't want to start replacing parts that may or may not be bad. Guess I'll just have to live with it for now.

**joebeer** · 05-26-2009, 04:28 AM

Originally Posted by allbaugh_04

I'm running on my last tank of 93 and it's tuned for it. None of the gas stations have 93 this year...I'm SOL

Allbaugh - I'm a contractor at Offutt AFB...I've been told that the T/A truck stop in Council Bluffs (I-80 exit 3) has 93 octane. I've seen it mentioned on several forums, some pretty recently. Other places mentioned include a Centex in Gretna and a Phillips 66 at 60th and Center in Omaha.

FYI: I found this thread by Googling "93 octane omaha"...planning to install CAI and retune my 07 Mustang GT this summer...want to use 93 octane, IF I can find it. I haven't had a chance to check any of these places out, so if you do, please post your findings.

**allbaugh_04** · 05-26-2009, 06:51 AM

Originally Posted by joebeer

Allbaugh - I'm a contractor at Offutt AFB...I've been told that the T/A truck stop in Council Bluffs (I-80 exit 3) has 93 octane. I've seen it mentioned on several forums, some pretty recently. Other places mentioned include a Centex in Gretna and a Phillips 66 at 60th and Center in Omaha.

FYI: I found this thread by Googling "93 octane omaha"...planning to install CAI and retune my 07 Mustang GT this summer...want to use 93 octane, IF I can find it. I haven't had a chance to check any of these places out, so if you do, please post your findings.

Ok, 60th and center isn't too far, i should be able to check that one soon. I have heard about the one in gretna but that is kind of a long haul.

Is it perhaps the yellow GT with black stripes?

**joebeer** · 05-26-2009, 02:15 PM

Nope, I'm all black with a Shelby-style aluminum grill and Flowmasters at the rear....planning white strips in the near future. Sometimes you can see it parked along the Martin Bomber Building ring road, but with all the parking lot and road work going on, I haven't driven it to work lately. I'm fortunate enough to have another car as my daily driver, so I keep the GT garaged during crappy weather, etc.