91 octane vs 87 fuel - Genesis Forum: GenCoupe Hyundai Genesis Forums
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#1 Old 12-29-2011, 08:31 AM
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91 octane vs 87 fuel

Hi guys just curious if anyone has tried the 91 octane fuel with better results than standard 87 octane. I have a 3.8L 2010 Track with an Ark Exhaust and CAI Injen. Just sitting at the gas station fueling up yesterday I always wondered about this question and whether or not it's worth adding 20 cents to gas prices.

I'm pretty sure this question has been asked before but I've tried doing the search and could not find any threads. If you can direct me to the thread that'll be great.

Thanks

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Last edited by mewang; 12-29-2011 at 08:44 AM.
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#2 Old 12-29-2011, 09:12 AM
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i think u do get better performance. i saw it in the 2013 thread.
ppl said u get 210 bhp with 87, while u get around 220 with 91?
idk someone confirm.
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#3 Old 12-29-2011, 09:23 AM
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You probably won't tell any difference between performance of 87/91. I personally been running 93 ever since I bought my car. I also had SFR tune my car to 93 when I got it flashed. You'll see people around this forum saying this or that but "f" it, if it's 20 cents more, then why not?

Also there's a ton of threads like these

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#4 Old 12-29-2011, 09:25 AM
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The fuel rating only makes a difference if you r engine would miraculously detect the octane, retune to adjust timing, fuel trim and possibly boost pressure to increase the pressure (compression) in the combustion chamber/cylinder. The octane rating basically let's you know how much you can squeeze the fuel before detonation, but will not cause any difference in performance unless 87 causes detonation and 91I doesn't which isn't in the case of our stock cars.

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#5 Old 12-29-2011, 09:28 AM
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For the cars who have had their ecu reflashed/tuned with higher boost then 91 would be needed.

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#6 Old 12-29-2011, 09:40 AM
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use search before starting new thread.
/thread
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#7 Old 12-29-2011, 09:41 AM
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Thanks for the responses. I actually found the other thread by googling it not using this search option but anyway they say that since they modded their cars like mine with the Ark Exhaust and Injen CAI 91-93, it could possibly show an improvement.

I'll give it a shot today and see how it feels. I've been driving on 87 ever since I've owned the vehicle and before the mods so I will sure be able to tell if there is a difference.

Thanks

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#8 Old 12-29-2011, 09:51 AM
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I just started using 91 octane for about a month and I haven't noticed any improvement in gas mileage or performance.

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#9 Old 12-29-2011, 09:53 AM
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I just started using 91 octane for about a month and I haven't noticed any improvement in gas mileage or performance.
Same with me. That's why Im back to 87.
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#10 Old 12-29-2011, 09:58 AM
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I will reiterate my point. A CAI and exhaust isn't going to be affected by octane because its not changing the overall cylinder pressure. When your cylinder pressure is increased during the compression cycle above stock then you would need a higher octane if you experience detonation. If you do not experience detonation you wont benefit from spending the extra money except having to carry a lighter wallet.

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#11 Old 12-29-2011, 10:00 AM
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Originally Posted by nobb View Post
Same with me. That's why Im back to 87.
it's already been dyno proven 93 offers more power, and i went from 87 to 93 and i noticed a difference. it takes about 2 fill ups first but there is a substantial difference. I noticed a difference

I am not a list of mods but what i know and share:
http://www.gencoupe.com/2-0t/94778-fuel-system-what-you-need-know.html
http://www.gencoupe.com/2-0t/86146-wastegate-101-a.html
http://www.gencoupe.com/2-0t/91199-compressor-maps-how-read-them.html

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I know you like making threads about these things that have been covered a ton, but this time, no.
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#12 Old 12-29-2011, 10:20 AM
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My mileage went up. The ECU DOES detect higher and lower octane from the knock sensor and adjusts the timing advance accordingly. Give it a tankful or more to adjust. My Stealth from 20 years ago did this! Hyundai advertises 223 HP with premium fuel, but most of their advertising is for regular fuel so as not to scare off potential customers. I use mid grade most of the time and I get better mileage. I think the alcohol raises the octane rating a bit too. In the hot summer months I often put 91 / 93 in. My tail pipes are cleaner and the engine does run better. I went back and forth to confirm better mileage and I now stick with higher octane as it more than pays for itself.



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#13 Old 12-30-2011, 06:46 AM
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those of u saying theres more power and better efficiency, prove it please. esp those throwing out hp numbers...

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#14 Old 12-30-2011, 06:48 AM
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i get better mileage
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#15 Old 12-30-2011, 07:06 AM
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Originally Posted by LOUISSSSS View Post
those of u saying theres more power and better efficiency, prove it please. esp those throwing out hp numbers...
The computer in the car "learns" if you are using better fuel. It will advance the timing to a predetermined max until it sees knock. More timing = more power, to a degree.
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#16 Old 12-30-2011, 07:24 AM
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As juice says... YES the ECU is designed to accept regular but it prefers premium. Manufacturer says so, that should be enough...


But there's more; many regions have ethanol in fuels at various percentages between up to %15 ethanol has high octane rating but contains much less energy per volume vs gas. Basically it's like watered down gas... (watered down with GMO corn fermented and distilled at huge environmental cost, to "save the environment..")

ethanol displaces oil and "cleans" your cylinder walls of it's protective film. Kills engines...

Around here it says right on the pump "may contain up to %10 ethanol" Some vendors know we don't like ethanol so they don't put any in their 91 octane; you'll see a sign 87 = up to 10% 89 up to 5% and 91 = no ethanol.

if at all possible, avoid ethanol.

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#17 Old 12-30-2011, 07:31 AM
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e85 is great I'm not sure what you're smoking, lol
If possible I'd like to run my car on e100.
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#18 Old 12-30-2011, 07:42 AM
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Originally Posted by Juice View Post
e85 is great I'm not sure what you're smoking, lol
If possible I'd like to run my car on e100.
Lots of things. None of which arw GMO...

E85 has very high octane therefore when you tune for it yields great power but you need a hell of a lot more of it to make that power than you would equally rated race fuel.

Its cost isn't really lower and it's social/environmental repercussions are just retarded...

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#19 Old 12-30-2011, 08:21 AM
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2.0t guys need to stop responding to a 3.8s question. Unless you own both engines dont reply like you know what you're talking about.

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#20 Old 12-30-2011, 08:23 AM
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Originally Posted by Snoopy0812 View Post
2.0t guys need to stop responding to a 3.8s question. Unless you own both engines dont reply like you know what you're talking about.
My response is universal

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