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Premium Fuel, Octane Rating


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10 replies to this topic

#1 ausubaru92

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Posted 22 November 2004 - 07:17 AM

I am somewhat confused:banghead:
Premium petrol has a higher Octane rating dosent it...?
Premium is supposed to increase performance isnt it...?
Octane is added to fuel to decrease pre-detonation (knocking) which means it contains a substance which reduces its ability to ignite
:drunk:


Please correct me if I am wrong on any of this as I have probably just got my wires crossed

Thanks

#2 Hocrest

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Posted 22 November 2004 - 07:37 AM

me too

Yep

Yep

Yep

#3 archemitis

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Posted 22 November 2004 - 09:19 AM

ok, if you have a low compression car, and you run premium gas, you car will be slower than if you were runing the cheap stuff.
its not more performance, the higher octane is harder to burn. thats why it doesnt pre detonate or ping as easily.
so if your using 91 octane in your 8:1 compression motor, stop, ,unless its a turbo.
also, we have 93 octane here, but its loaded with about 10 %ethanol. which makes my 11:1 harley ping like crazy.

#4 Vanislru

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Posted 22 November 2004 - 01:09 PM

Premium 92 = 92 parts octane 8 parts heptane
regular 87 = 87 octane 13 parts heptane.

Heptane has a lower ignition temperature, octane has a considerably higher.
regular has more power but ignites at a lower temp, this is why high comp, turbo and supercharged motors need premium. All that compression makes for more heat and a higher likelyhood of autoignition so a higher octane is needed.
Some gas suppliers pull from the same tank[s] and use an additive to bring the octane rating up. It is just a rating. It doesn't mean that there is physically 87 parts octane and 13 heptane, it means they have produced something with the same characteristics/rating.

That "peformance" comes from the additives and the performance they are speaking about is cleaner combustion chambers and valves, etc. 'They' would like you to think more power but that's not the case. Notice they always say performance not power. Regular has more power.
If you can run reg. it's better.
Those additives are bad news, and for those in the midwest try to use Shell it comes from better [more modern less cat clogging sulfur and other nasties] refineries than others. Unless you know a chain that brings there supply from the coast.
This comes from talking to the techies in the refineries I worked in, Shell, Exxon/Esso, Syncrude, Suncor, Petrocan, etc.

just my 2 cents

#5 naru

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Posted 22 November 2004 - 01:56 PM

I am somewhat confused:banghead:
Premium petrol has a higher Octane rating dosent it...?
Premium is supposed to increase performance isnt it...?
Octane is added to fuel to decrease pre-detonation (knocking) which means it contains a substance which reduces its ability to ignite
:drunk:


Please correct me if I am wrong on any of this as I have probably just got my wires crossed

Thanks



Yes,No and No.
Higher octane gas contains slightly less BTUs/litre.
Higher octane gas isn`t harder to ignite or burn,it is merely more detonation resistant.

#6 Vanislru

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Posted 22 November 2004 - 03:55 PM

Nice links guy. :grin:

#7 naru

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Posted 22 November 2004 - 04:22 PM

[quote name='Myxalplyx']"High performance cars actually take advantage of the fact that 93 octane is harder to burn. These cars are able to have higher compression ratios and more performance oriented ignition timing curves. Where as in most cars that just require 87, no real benefits can be had from using higher octane gas and actual harm may occur."
"And secondly, you can end up clogging your engine with harmful carbon deposits and possibly lower your gas mileage. This is because the higher octane is harder to burn, and lower performance engines may not be able to completely burn all the gas, which causes carbon to build up."
http://www.epinions....tent_2618204292


"Did you know that high-octane gas is not more powerful than regular gas — and that it's actually harder to burn?"
http://www.m-emag.co...&article_id=517


"The higher the octane number the harder it is for the fuel to start burning. This reduces the chance that a hot spot, in the combustion chamber, will pre-ignite, causing pinging."
http://www.dansmc.com/gas.htm


Your sources are laughibly ignorant.Epinions? Come on.
Why don`t you try reading something from someone who actually knows what they are talking about?
http://www.faqs.org/...3/preamble.html

Quote Originally Posted by ausubaru92
Premium petrol has a higher Octane rating dosent it...?
Thanks


"It depends! For the most part the answer will be no."

HUH?? A higher octane rating is the definition of premimum gas.

#8 Vanislru

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Posted 22 November 2004 - 04:57 PM

Laughibly ignorant?? Ouch. He just posted links, if they're that bad state how.
Your link was a good read.
Premium gas will not neccesarily have x amount of octane, it might have x amount + additives that give it the stated #.
How do you suggest gas stations run out of reg, reg+, and premium at the same time?
Premium gas= performance, sort of if you have the engine that requires it but not for your average engine, and most likely not for modern ones.

#9 naru

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Posted 22 November 2004 - 05:48 PM

Laughibly ignorant?? Ouch. He just posted links, if they're that bad state how.
Your link was a good read.
Premium gas will not neccesarily have x amount of octane, it might have x amount + additives that give it the stated #.
How do you suggest gas stations run out of reg, reg+, and premium at the same time?
Premium gas= performance, sort of if you have the engine that requires it but not for your average engine, and most likely not for modern ones.


If you read the gasoline FAQ it is obvious.
The author makes the point,ad naseum,that octane rating is a measure of detonation resistance.Nothing more,nothing less.
Octane rating is what we are talking about,not octane content.If you want to know about octane content read part 2 of the FAQ.
Don`t recall suggesting anything about gas stations.
Premimum gas=more power only in the sense that it helps avoid detonation in some engines.
Plenty of modern engines require premimum.Buddy`s Honda SIR springs to mind.

#10 archemitis

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Posted 22 November 2004 - 10:05 PM

ug gas. resisting detonation is the same as not burning as easliy, or however you want to word it.

#11 Ross

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Posted 22 November 2004 - 11:01 PM

higher octane= higher self ignition temp, therefore better detonation resistance. Detonation occurs when a reigon of the fuel/air mixture excedes the self ignition temperature of the fuel, either because of too high compression, or from being near a part of the engine that is too hot, ie if you use a spark plug with the wrong temp rating.




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