Why 91?

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scarface
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Why 91?

Post by scarface »

Just wondering why they have 91 octane since no car (that I know of) requires it.I've only seen requirments of 87 or 93.NowI understand I Cali that they don't have 93 or something like that,but wouldn't that be hurting all those cars that require 93 and simply cannot accept 91.Also,if a car is made for 87 oct (ex. 98 corolla),would it do any good to choose 91 over 87 (now I think I read somewhere else in this forum that 93 in such a car would actually hurt it so I'm not asking about that)?
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Post by potownrob »

There's no point putting 91 or 93 in your car as youe engine has too low a compression ratio to benefit from anything better than 87. I don't remember why they have both 91 and 93 at some places, but I do know that some cars recommend 91 (such as my Maxima) while some require 93. I still put in 93 when I find 91, since people on maxima.org claim to get better gas mileage with the 93 for just 5 cents more per gallon, plus I'm not a granny behind the wheel :twisted:
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Post by jcprov21 »

My user manual tells me to ONLY put 87 in mine.....
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Post by s4rge »

jcprov21 wrote:My user manual tells me to ONLY put 87 in mine.....
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Post by VTECaddict »

all the cars that ive seen that require premium fuel say 91 octane or higher. ive never seen one that says 93....
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Post by blaze0303 »

its all about anti knock and ignition timing...my car needs to run 93 or higher because of the turbocharger, if i was to run anything lower it would knock.
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Post by Johnf514 »

Many cars require 91 octane. Anything with a high performance engine (think Lexus, Infiniti, Acura, Audi, etc.) will run on this cleaner fuel in order to gain the necessary power to perform and run at their peak.
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Post by LS1Leader »

I always thought most cars were tuned for 91 octane, since that's all we have here in CA... Then again, there's a few car models which are "california-only", meaning that the other 49 states get one car, and californians get one with some tweaks for emissions purposes, etc. Some CA-only cars also mkae less power.
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Post by Standardshifter »

I've seen 91 octane recommended for cars and I've seen 91 required for cars.

For example, in the case of Subaru, 91 is required for the turbo models, recommended for those with the H6.
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Post by LS1Leader »

IIRC, my H6 required it.
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Post by Tiamat »

Scarface, the octane number is only a measure of how much you can compress the stuff before it spontaniously ignites. Putting higher octane gasoline in a car that doesn't require it wouldn't do you any good unless you had reason to belive the compression ratio of your engine had gotten higher. It shouldn't make any difference in gas mileage or anything, in theory. It might, for all I know, because all I've learned is theory, but it shouldn't.

LS1Leader: 91 is all we have in Cali? I just filled up with 87 yesterday...
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Post by IMBoring25 »

I've never seen 93 required for a factory street car. Chipped/modded cars, yes, but not a factory street car.
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Post by LS1Leader »

Tiamat wrote:LS1Leader: 91 is all we have in Cali? I just filled up with 87 yesterday...
As in, 91 is the highest that's regularly available at most pumps.

EDIT: Now that I re-read my first post, I was being an idiot and wasn't very clear. I meant that for cars that were marked as needing premium fuel, that I expected those cars to be tuned to 91 octane vs. 93 octane.
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Post by scarface »

most luxury cars require premium fuel only and turbocharged cars do also to prevent knock
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Post by Sypher »

hmm i've always thought that the higher the octane the better.. :S i knw now lol...

but did u know in japan, they have like up to octane 106 or sumtihng... crazyiness....
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