Tonylmiller

I've been putting 91 octane in my 2006 LS2, but the consensus around here seems to be that 93 octane is required for the engine to run best. Apparently some people have checked this out in detail and I do not doubt it.

However, I wonder why Chevy would put 91 octane in the manual? There must be a reason. Does anyone have any ideas?

sallen619

CA only goes up to 91...

BadgeZ28

Well all of the local stations I buy from only have 91. It is my understanding they will also run on 87 with reduced performance. 93 might be a region or vendor specific fuel?

Joezone914

In some parts of the country high test only goes to 91.

Tonylmiller

Even so, I would still think they would let the owners know that 93 is best. One can always use an octane booster if needed.

Vette_DD

The 2006 owner's manual actually says 91 octane or higher.

LSD 2005

Tonylmiller

No doubt, higher octane will work, but why wouldn't they say 93 instead of 91?

Rick 98

I have traveled the west coast, rockies a lot last year or so, have not seen anything higher than 91. 'sometimes they only have 85, 87, & 89 East of Idaho/Nevada. Rick

Vette_DD

As others have said, probably because of CA.

at7000ft

Like high altitude places like Colorado.

TLS_Addict

Local place has Ethanol free 91 octane. Its what I try to fill up with if I can.

Steve_R

Because it will run fine on 91.

Maybe GM is trying to keep you from wasting money on 93 thinking it will run "better."

Vette5.5

Higher compression ZO6 manuals mention 93 octane recommended for best perfomance, but 91 is ok, as all many states have. Keep in mind, LS7's only meet the 505 hp rating on 93 octane at sea level. Less octane pulls timing, and every 1000 ft altituded thinner air, loses 3% power, so why 5000 ft in the mountains, fuel requirement's are lower. Figure a 505 hp LS7 at sea level, will only be 420 hp in CO. Turbo, supercharged cars, are real champs in the mountains. The 91 octane max in CA is a good one too. Seems you need further refining to get get 91 to 93, yielding a Few percent less of final product, per crude input.

Gearhead Jim

My informal observations suggest that most 93 octane has ethanol (which raises the octane number), and most no-ethanol gas tops out at 91 octane. I'm sure there are exceptions...

HOXXOH

Max 91 octane and no ethanol-free in AZ.

Tide Will Roll!

Around here the only places that have the No Ethanol are not "Top Tier"

Bert

Roll Tide!

383vett

If the manual said "use 93", what would owners think or do if all that was available was 91?

jb_va2001

Exactly.

Audacious Nick

Do you understand how much octane booster would be required to raise the octane rating of a full tank of fuel, by two? Each point they claim only adds 0.1. So if it says it will raise a full tank by 5 points, you will have 91.5 fuel. So you will need 4 bottles of octane booster to raise it from 91 to 93, assuming each bottle raises it by 5 points.
Looking at the cost of a bottle of octane booster, that's going to cost you a pretty penny every fill-up.

Back to the subject, they put 91 octane because that is the highest octane offered in some areas of the U.S. And putting 93 might confuse some people that purchase it there. So to avoid the stupid questions, they put 91 minimum.