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Old 07-06-2014, 04:49 PM   #1
njshred
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Default Shell 91 or Chevron 94?

I have a 2013 STI just flashed to cobb stage 1 91 octane. Which is best for our subies, shell 91 or chevron 94? been getting mixed opinions
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Old 07-06-2014, 05:15 PM   #2
Wrgb
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I have Heard mixed opinions as well.

Apparently usa shell 92 is best.
But without crossing the border...

I'd love to switch to shell 91 if it's not gonna be bad for the sti. Go back to getting air miles and bigger smiles.
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Old 07-06-2014, 06:04 PM   #3
on9
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shell 91 seems to not knock as much as chev94...
atleast on my car..
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Old 07-06-2014, 08:50 PM   #4
JordanF
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I've always used Chev 94 in my vehicles, interested to see how people like shell gas though
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Old 07-06-2014, 11:18 PM   #5
hi-revs
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Im tuned to 93 octane.
been using chevron 94 and have had no issues
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Old 07-07-2014, 12:19 AM   #6
njshred
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Quote:
Originally Posted by hi-revs View Post
Im tuned to 93 octane.
been using chevron 94 and have had no issues
In the cobb map notes it says ppl using canadian 94 gas should use the 91 map because their maps are done using gas with ethanol. Our premium fuel in canada doesnt contain ethanol. But if youve been using a 93 map with no issues thats good, maybe ill do a couple logs with it and see how they look.
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Old 07-07-2014, 10:01 AM   #7
mrjason
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Shell 91 is rumored to be better than Chevron 94.

Right now my tank has Chev 92 from the US.

im going to be using shell 91 to see if my car is ok on it, once I run out of my current tank.
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Old 07-07-2014, 11:31 AM   #8
danny_d19
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Please update the thread with your findings. Last year after getting an e-tune on chevron 94 I tried a few tanks of shell 91 and did not notice a difference, but switched back to 94 (not sure exactly why, but I did).

Going to try switching back again to see how it goes now that I have a v3 AP and can more easily view realtime data
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Old 07-07-2014, 11:59 AM   #9
mrjason
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I don't have a cobb - so I go by butt dyno lol.
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Old 07-07-2014, 12:53 PM   #10
S38B36
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I'm having a hard time understanding how 91 octane of any type can consistently offer more performance than Chev 94..

Can anyone provide the actual science behind this? Not understanding how 91 w/ 10% ethanol can offer more resistance to detonation than 94 w/o ethanol.

I would imagine that there are some legitimate issues with "old" 94 sitting in the Chevron tanks, due to insufficient sales volumes / turnover.

Just seems very strange to me that 91 w/ ethanol can be in any way superior to 94 straight gasoline in terms of resistance to detonation.. assuming of course the 94 has not degraded from sitting.

Has anyone seen any more specific documentation of this issue?

Cheers
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Old 07-07-2014, 12:59 PM   #11
njshred
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I seem to be getting more bad tanks of chev 94 lately. I got some in coquitlam last and it definately seems like a bad batch.
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Old 07-07-2014, 01:01 PM   #12
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Old 07-07-2014, 01:55 PM   #13
Lionscage
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I have an older (99) JDM and I haven't got in my ECU to see what, if anything, it's tuned to/for/at all. So far, I've only used Chev 94 and it seems to run pretty well. No noises from under the hood. Was considering giving Shell a try but is there really any point if I'm running strong on Chev 94?

Should I give Chev 91 w/eth a go?

Last edited by Lionscage; 07-07-2014 at 02:11 PM.
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Old 07-07-2014, 02:51 PM   #14
njshred
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Quote:
Originally Posted by Lionscage View Post
I have an older (99) JDM and I haven't got in my ECU to see what, if anything, it's tuned to/for/at all. So far, I've only used Chev 94 and it seems to run pretty well. No noises from under the hood. Was considering giving Shell a try but is there really any point if I'm running strong on Chev 94?

Should I give Chev 91 w/eth a go?
I dont think shell 91 has ethanol either. Hows your car running? And how do you find rhd? Im thinking of going JDM. Less than half the price, more freedom lol. Just kinda sketched out about reliability and rhd.
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Old 07-07-2014, 02:52 PM   #15
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Shell has ethanol, at least it does here in the northeast. It's just top tier which means it has more detergents than non top tier fuel companies
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Old 07-07-2014, 03:10 PM   #16
Lionscage
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Quote:
Originally Posted by njshred View Post
I dont think shell 91 has ethanol either. Hows your car running? And how do you find rhd? Im thinking of going JDM. Less than half the price, more freedom lol. Just kinda sketched out about reliability and rhd.
Love my JDM. I have no problem with the RHD. A little more caution and patience with left hand turns and you're all good. As long as you buy from a reputable JDM delaer/importer I would say reliability would be better than NA LHD models. Just depends on previous owner/s on either side of the ocean.

Sourcing parts for when you need to replace something as minor as spark plug wires or in my case, a radiator can take on a whole new life with a JDM.
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Old 07-07-2014, 03:13 PM   #17
kavid dobayashi
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I've been using chev 94 with the cobb stage 2 93 map for ages now, never had an issue. Prior to going to stage 2 I think I used the stage 1 93 map and never had an issue on chev 94 either.
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Old 07-07-2014, 10:34 PM   #18
danny_d19
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Do you log regularly?

When I read "never had an issue" I read "my engine hasn't exploded", but it could be experiencing detonation at various times and you just don't know
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Old 07-08-2014, 01:24 AM   #19
njshred
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Yeah they make those maps on gas with ethanol. Our fuel isnt up to par with theirs
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Old 07-08-2014, 11:49 AM   #20
mrjason
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My stock car running Chevron 94 knocked on the dyno when building boost.
Due to bad fuel.
Knock went away on American 92 Chevron.

So if you arent looking for it - you wont find it.

FYI - Fuel Lights on - ill give Shell a go today.
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Old 07-08-2014, 12:59 PM   #21
tabruder
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Quote:
Originally Posted by mrjason View Post
I found this too when researching fuel when I got my wrx. Apparently a few reputable PNW tuners had to pull several degrees of timing on the same car when running Chev94 vs US 91/92.

My old 08 2.5i had huge (for n/a) gains being e-tuned for chev 94, but that was coming from the stock 87+ map, and the turbo engines add a whole new element.

All parts of BC I've been to have Shell 91 with no ethanol.

Elsewhere on nasioc/cobb pages (no links handy, sorry) I was consistently reading that our engines really like the ethanol for having cooler ignition temperatures for a given octane rating, giving better resistance to knock.

I'd be very interested if anyone had some dyno or road tune evidence for knock threshold with Chev 94(0%) vs Chev 91(10%) vs Shell 91(0%).
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Old 07-08-2014, 01:49 PM   #22
Lionscage
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Too bad I just filled up yesterday but I guess next tank will be Chev 91 with the 10% Eth and see what ye old butt dyno says. That'll be the tank my engine grenades lol
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Old 07-08-2014, 03:10 PM   #23
mrjason
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I was actually thinking of going to Chevron today instead. I gotta run to the airport and chevron is the closest station again.

Ill just put in a 1/2 tank maybe and see what happens.
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Old 07-08-2014, 03:58 PM   #24
njshred
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Im gonna try chevron 91 next
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Old 07-08-2014, 10:10 PM   #25
clsmooth
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Tuned on Chevron 94 for years, never an issue...
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