Welcome to the North American Subaru Impreza Owners Club Sunday November 23, 2014
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC Technical > Normally Aspirated Powertrain

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads.
Reply
 
Thread Tools Display Modes
Old 03-12-2003, 07:19 PM   #1
Nemnith
Scooby Newbie
 
Member#: 30973
Join Date: Dec 2002
Vehicle:
2001 Impreza
Gray

Question Real Deal on Octane

Hey everyone. I've heard a few different things about what type of gas people put in their cars. I've heard stuff like "as low octane as possible without knocking" and "higher octane the better." Anyone care to shed some light on exactly which I should be using in my '01 2.5RS? I'm using Super (89 octane) at the moment, but I've been hearing that it's a waste of money. Thanks.
* Registered users of the site do not see these ads.
Nemnith is offline   Reply With Quote
Old 03-12-2003, 07:39 PM   #2
joefocker20
Scooby Specialist
 
Member#: 13745
Join Date: Dec 2001
Chapter/Region: RMIC
Location: Colorado Springs, CO
Vehicle:
2004 STI
Silver

Default

Well, Ive been putting 89 in my car, but I have a PROECM and should be putting in 91 for optimal power. Within the next few months, when I get most of the stuff I want for my car, I'm going to dyno it, and I'm going to put 93 in for that. Put the cheapest gas you can in right now, the prices are outrageous..
joefocker20 is offline   Reply With Quote
Old 03-12-2003, 08:18 PM   #3
sti27
Scooby Newbie
 
Member#: 33715
Join Date: Mar 2003
Location: York,Pa
Vehicle:
98 2.5rs
rallyblue pearl

Default

Im no expert on gas, but what I learned is the higher octane (92,93,94) will help keep alot of stuff inside the engine clean. Kinda eliminating the need for fuel injection cleaner. My local Sunoco sell GT100 octane fuel and of course I had to try it.
It was $3.50 a gallon(last year sometime, Im sure its more now)
and cost me $25 for only have a tank. Wouldn't recommend buying all the time for the price, but I did notice a difference.
sti27 is offline   Reply With Quote
Old 03-12-2003, 08:41 PM   #4
ciper
Scooby Guru
 
Member#: 15543
Join Date: Feb 2002
Location: san francisco, ca
Vehicle:
90BJ Legacy LS ABS
AWD 946 Rio Red Jpn built

Default

sti27: Although Im a strong supporter of higher octane for some people I think the "cleaner" idea has been proven wrong. The fuels are basically equal in all respects except the higher octane is slightly more stable.

If all you do is putt around using at most 30% throttle 85 octane would probably be good enough.

However if your car calls for 87 and you run it in hot weather at WOT half the time it would still benefit from 92.

What Im trying to say is higher octane may be better but not everyone needs it
ciper is offline   Reply With Quote
Old 03-12-2003, 10:12 PM   #5
Supraru
Scooby Specialist
 
Member#: 23313
Join Date: Aug 2002
Location: Collegeville,Pa
Vehicle:
99' 2.5Rs
black

Default

I use moble 93 everytime I fill up. If I switch back my car will probably run crappy. Plus I usually don't put around, I'm always driving hard.
Supraru is offline   Reply With Quote
Old 03-12-2003, 11:58 PM   #6
meZoom!
Scooby Newbie
 
Member#: 33915
Join Date: Mar 2003
Location: everywhere in Los Angeles
Vehicle:
2003 Impreza 2.5RS
silver

Default

(hey my first post here!)

In most Japanese cars I tend to pump in 91 octane (currently the highest available in so cal). My cousin in japan works at a gas station and he told me that the LOWEST octane they sell there is 92 or 93, i forget which, and the highest they sell is 100. keep in mind this is a normal station in a normal town. after hearing that, i got to thinking that perhaps japanese cars, at least, are designed with this in mind.
meZoom! is offline   Reply With Quote
Old 03-13-2003, 12:22 AM   #7
JohnP555
Scooby Newbie
 
Member#: 20355
Join Date: Jun 2002
Location: Worcester, PA
Vehicle:
99 RS
Rally Blue Pearl

Default

Yeah I as well am not really sure how the octane thing works. I was under the impression that all fuels had the same clean factor and that running 93 in a car designed to run 87, such as the RS, would do absolutely nothing you would be throwing your money away. Anyone have information on any studies done on this or what?

I have run 87 in my car since day one, haven't really felt a need to run a higher octane. Then again I don't putt around town, so maybe I would benefit from an octane increase at the pump.
JohnP555 is offline   Reply With Quote
Old 03-13-2003, 12:33 AM   #8
zzyzx
Scooby Specialist
 
Member#: 815
Join Date: Jan 2000
Location: Florida
Vehicle:
2013 Boss 302 White
2000 2.5 RS Coupe Silver

Default

Quote:
Originally posted by meZoom!
(hey my first post here!)

In most Japanese cars I tend to pump in 91 octane (currently the highest available in so cal). My cousin in japan works at a gas station and he told me that the LOWEST octane they sell there is 92 or 93, i forget which, and the highest they sell is 100. keep in mind this is a normal station in a normal town. after hearing that, i got to thinking that perhaps japanese cars, at least, are designed with this in mind.
In Japan octane is rated in RON. Do a search for explanations.

I collected some data with a data logger at the race track comparing 87 vs. 92 and the timing curves using the stock ECU were more advanced with 92. This was on a '00 2.5 RS.

- Steve
zzyzx is offline   Reply With Quote
Old 03-13-2003, 04:04 AM   #9
karl_hungus
Scooby Newbie
 
Member#: 7507
Join Date: Jun 2001
Location: Windsor, Ontario
Vehicle:
2002 WRX Wagon
PSM

Default

I wouldn't waste the money by putting in high-octane all the time. If you plan to head to the strip or autox and you want more protection against knock then buy the expensive stuff otherwise you're throwing money away.

I've run my car hard in the heat with 87 octane with no perceivable knock... although I got my ECU mapped for 92 octane last fall so thats all I run now.
karl_hungus is offline   Reply With Quote
Old 03-13-2003, 09:40 AM   #10
Legacy777
Scooby Guru
 
Member#: 4800
Join Date: Mar 2001
Chapter/Region: TXIC
Location: Houston, Tx
Vehicle:
1990 Legacy & 97 OBS
AWD 6MT EJ22T AWIC Swap

Default

This subject has been beat to death many times on this board and others. There are some basics that need to be understood when "tackling" the octane issue.

The quick answer is that higher octane is not always better, and it will vary for different motors, different ECU's, different driving styles, etc.

Now lets get a little more technical. The octane rating essentially refers to the amount of energy needed to ignite fuel. 92 octane will require more input energy before it ignites then 87 octane.

Most cars are designed to run on 87 octane. They're timing curves and everything are set around that. If you put higher octane in there and the ECU does not know it's higher octane. It really doesn't know it can advance the timing further to get more power and not have to worry about knock.

Yes the ECU can learn over time, but from personal experience and from others that have done similar tests, the extra power that you seem to get from that first tank or two of higher octane seem to go away and your car feels the same. Yes i know that's not a very scientific test, but I know I've done the test several times and every time I come away with the same conclusions.

What auto manufacturers need to do is do what Polaris did on their snowmobiles. Have a switch you can flip that tells the ECU you have premium in, so it can take advantage of the higher octane.

There are few other points I could make, but don't have time for that now.

Personally.....I run 89 octane. The car just seems to run best on it. Don't ask me why....it just does.

Other's may have similar or different experiences with what their cars likes, but what I said are the principles behind the whole octane thing and how the computers are setup.

Josh
Legacy777 is offline   Reply With Quote
Old 03-13-2003, 11:40 AM   #11
BOY
NASIOC Supporter
 
Member#: 232
Join Date: Sep 1999
Chapter/Region: MWSOC
Location: Ft Wayne, IN
Vehicle:
99 RS-T RIP
02 Forster-S

Default

Read up: http://www.refiningonline.com/Engelh...ep/TCR4_29.htm

Octane is literally resistance to detonation (any detonation). The higher the octane the harder it is to explode the air fuel mix. RSs were designed for 87 PON (pump octane number or [RON+MON]/2) and will advance timing some with higher octane but unless you're running aftermarket electronics (fuel and/or timing control) or cams/FI your better off rolling up your dollar bills and stuffing them into your gas tank.
BOY is offline   Reply With Quote
Old 03-13-2003, 11:42 AM   #12
DanzBorin
Subaru Bounty Hunter
Moderator
 
Member#: 7131
Join Date: Jun 2001
Chapter/Region: TXIC
Location: Houston - Back in the Alief
Vehicle:
2008 STi DGM (3rd
STI) prev 05 STi (white)

Default

Quote:
Originally posted by BOY
unless you're running aftermarket electronics (fuel and/or timing control) or cams/FI your better off rolling up your dollar bills and stuffing them into your gas tank.
make sure to put some sugar in there too*...



*disclaimer: don't do this, and if you do you are stupid and deserve whatever happens...
DanzBorin is offline   Reply With Quote
Old 03-13-2003, 11:49 AM   #13
BOY
NASIOC Supporter
 
Member#: 232
Join Date: Sep 1999
Chapter/Region: MWSOC
Location: Ft Wayne, IN
Vehicle:
99 RS-T RIP
02 Forster-S

Default

Danz talkin trash
BOY is offline   Reply With Quote
Old 03-13-2003, 12:05 PM   #14
DanzBorin
Subaru Bounty Hunter
Moderator
 
Member#: 7131
Join Date: Jun 2001
Chapter/Region: TXIC
Location: Houston - Back in the Alief
Vehicle:
2008 STi DGM (3rd
STI) prev 05 STi (white)

Default

Quote:
Originally posted by BOY
Danz talkin trash
I just had a vision of people stuffing dollars into their gas tank...

I figured if you could talk them into doing that, sugar would be the next logical step...
DanzBorin is offline   Reply With Quote
Old 03-13-2003, 05:33 PM   #15
Jack
Add Lightness
Moderator
 
Member#: 13699
Join Date: Dec 2001
Chapter/Region: NESIC
Location: Hopkinton, MA
Vehicle:
2007 Lotus Elise
(From General)

Default

The octane ratings at the pumps are MINIMUMS. A few years ago, it was disclosed by Sunoco that their 86 octane in most markets (including New England) was actually 87. They then removed 86 from all their pumps.

I've run 87 in all my cars for 20 years on the street and 91 or 93 on track days only. Cars have included 90 M3, A4 5valve V6, Dodge Turbo, Honda 1.6L 16Valve. None have pinged or ever had an engine failure. I've saved a lot of money over the years not going to higher octane. In my 91 CRX manual and wife's 91 Integra manual, Honda expressly stated that running anything over 87 octane is a waste of money and will get you no better performance.

When a car says "premium fuel only", it's because they needed it to meet EPA emissions requirements.

jack
Jack is offline   Reply With Quote
Old 03-13-2003, 09:19 PM   #16
Legacy777
Scooby Guru
 
Member#: 4800
Join Date: Mar 2001
Chapter/Region: TXIC
Location: Houston, Tx
Vehicle:
1990 Legacy & 97 OBS
AWD 6MT EJ22T AWIC Swap

Default

Just to throw this tid-bit out.....

My car actually seems to have less power with premium vs. 89 octane......so computers/engines will vary
Legacy777 is offline   Reply With Quote
Old 03-13-2003, 11:51 PM   #17
slowlegacy
Scooby Newbie
 
Member#: 30507
Join Date: Nov 2002
Location: maryland
Vehicle:
94 legacy
green

Default

run a tank of 87, 89, and 102 through to see what you think. keep in mind you'd get better performance putting your foot 15% further on the petal with cheap gas than getting gas that costs 15% more.
slowlegacy is offline   Reply With Quote
Old 03-14-2003, 12:06 AM   #18
slowlegacy
Scooby Newbie
 
Member#: 30507
Join Date: Nov 2002
Location: maryland
Vehicle:
94 legacy
green

Default

i said that wrong. if you drive hard enough to burn 15% more gas, the car will definately feel faster
slowlegacy is offline   Reply With Quote
Old 03-14-2003, 09:28 AM   #19
Legacy777
Scooby Guru
 
Member#: 4800
Join Date: Mar 2001
Chapter/Region: TXIC
Location: Houston, Tx
Vehicle:
1990 Legacy & 97 OBS
AWD 6MT EJ22T AWIC Swap

Default

I don't quite get what you're saying??

Are you saying that if you put the cheap stuff in, you'll have to push the gas pedal 15% more then what you would with more expensive stuff?
Legacy777 is offline   Reply With Quote
Old 03-14-2003, 02:47 PM   #20
ciper
Scooby Guru
 
Member#: 15543
Join Date: Feb 2002
Location: san francisco, ca
Vehicle:
90BJ Legacy LS ABS
AWD 946 Rio Red Jpn built

Default

I think he is just crazy.

Ive literally used about 1000 gallons of 91 octane in my Legacy that asks for 87 and I still do it.
ciper is offline   Reply With Quote
Old 03-14-2003, 04:56 PM   #21
RebelINS
Scooby Specialist
 
Member#: 2953
Join Date: Nov 2000
Chapter/Region: MWSOC
Location: Rochester, MI, USA
Vehicle:
2000 Impreza 2.5RS
2005 Impreza WRX STi

Default

I have tried running pretty much every octane gas that the average pump offers, and I have never really noticed any difference. Now I just run plain old 87 because I didn't notice any difference when I was running other octanes, plus gas prices a getting pretty high now.

-Wes
RebelINS is offline   Reply With Quote
Old 03-15-2003, 12:32 AM   #22
yamahito
Scooby Newbie
 
Member#: 31908
Join Date: Jan 2003
Chapter/Region: South East
Location: Greenville, SC
Vehicle:
1999 Impreza RS
Rally Blue

Default

My findings in short:

Lower octane detonates easier, if you put a higher octane it will not detonate as efficiently and may leave carbon deposit buildup in your engine (so actually using higher octane may be more 'dirty' for your engine).

Higher compression engines e.g. WRX are compressing the gas to the point where 87 octane may predetonate (remember, it detonates easier). This is the reason they need higher octane.

Bottom line is that higher octane in an RS will actually make it run less efficient and cause more buildup.

I gathered this info from several mechanics, drag racers, and I was very skeptical, but believed them after reading many articals/ websites on this. There is a pretty good explanation on howstuffworks.com go under auto, then how engine works. Great website.
yamahito is offline   Reply With Quote
Old 03-15-2003, 04:16 AM   #23
RebelINS
Scooby Specialist
 
Member#: 2953
Join Date: Nov 2000
Chapter/Region: MWSOC
Location: Rochester, MI, USA
Vehicle:
2000 Impreza 2.5RS
2005 Impreza WRX STi

Default

Quote:
if you put a higher octane it will not detonate as efficiently
I think you misused the word detonation. You don't want more efficient detonation, you don't want any detonation, detonation is bad. I think you meant it won't burn as efficiently, but I am not 100% sure that that is true. The octane number is based on the knocking tendencies of the hydrocarbons heptane and isooctane. Heptane is sort of the base for the scale because it has a higher tendency to knock then normal gasoline. Isooctane is given the octane number of 100 because of it's resistance to knocking in comparison to commercial gasoline. If the octane number is under 100 it represents the percentage of isooctane that is mixed with heptane to give bordeline detonation with the same conditions as the base fuel. If the number is over 100 it indicates the mililiters of tetraethyl lead that is added to isoocatane to knock the same as the base fuel. It really isn't the most scientific scale ever created. I don't think though that just because there is a higher octane number that the fuel won't burn as efficiently though, but maybe I am wrong about that.

-Wes
RebelINS is offline   Reply With Quote
Old 03-16-2003, 12:04 AM   #24
meZoom!
Scooby Newbie
 
Member#: 33915
Join Date: Mar 2003
Location: everywhere in Los Angeles
Vehicle:
2003 Impreza 2.5RS
silver

Default

i was so moved by this thread that i accidentally on purpose pumped in 89 instead of my usual 91 and see no difference, or actually kinda like it.
meZoom! is offline   Reply With Quote
Old 03-17-2003, 08:09 AM   #25
nixx
Scooby Newbie
 
Member#: 7581
Join Date: Jun 2001
Location: Toronto, ON
Vehicle:
2001 Impreza 2.5RS
Silver

Default

Quote:
Originally posted by yamahito
My findings in short:

Lower octane detonates easier, if you put a higher octane it will not detonate as efficiently and may leave carbon deposit buildup in your engine (so actually using higher octane may be more 'dirty' for your engine).

Higher compression engines e.g. WRX are compressing the gas to the point where 87 octane may predetonate (remember, it detonates easier). This is the reason they need higher octane.

Bottom line is that higher octane in an RS will actually make it run less efficient and cause more buildup.
Replace 'detonate' with 'combustion' then now I agree 100%!

Plus why can't ppl take a look at their owners manual because it clearly says to put regular (87) for 2.5RS and premium (91-94) for WRX. If you're stock just go by those guidelines unless you have some engine management to advance the timing.
nixx is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
The REAL deal on under/overpowering drivers Daishi00 Car Audio, Video & Security 66 02-23-2007 11:02 AM
The real deal on the borla header craze lately? (considering one) overdose Factory 2.0L Turbo Powertrain (EJ Series Factory 2.0L Turbo) 7 10-04-2004 06:06 PM
STi Lights on ebay...are these the real deal? SILVERWRXWAGON Interior & Exterior Modification 12 11-29-2001 08:34 AM
what's the real deal on headers (equal length vs. borla) FormerSubTech Normally Aspirated Powertrain 17 11-06-2001 11:38 PM
DEALS on some REAL parts. chris300zxtt Tri-State Area Forum 5 10-02-2001 04:00 PM


All times are GMT -4. The time now is 06:13 PM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2014 Axivo Inc.
Copyright ©1999 - 2014, North American Subaru Impreza Owners Club, Inc.