What octane to use - Subaru Forester Owners Forum
View Poll Results: The best octane for stock 99 Forester S 2.5
87 33 60.00%
89 8 14.55%
91 13 23.64%
ULTRA 94 2 3.64%
Multiple Choice Poll. Voters: 55. You may not vote on this poll

User Tag List

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
post #1 of 16 (permalink) Old 05-11-2008, 07:31 PM Thread Starter
Registered User
 
lukesforester's Avatar
 
Join Date: May 2008
Location: verona ont. canada
Posts: 47
Car Year: 1999
Car Model: forester s
Gallery: 0
Feedback Score: 0 reviews
What octane to use

Hey i just got my forester, I've heard there 10:1 compression ratio.
To me that seems high so would i get better mpg and or better performance from higher octane gas, 89,91 or even ultra94... i work at sunoco lol
lukesforester is offline  
Sponsored Links
Advertisement
 
post #2 of 16 (permalink) Old 05-11-2008, 07:41 PM
Smart Cookie
 
RocketEyes's Avatar
 
Join Date: May 2007
Location: Oklahoma City
Posts: 3,084
Car Year: 2007
Car Model: Forester XT Sport
Gallery: 0
Feedback Score: 4 reviews
Especially if you have a turbo..nothing less than 91. If I could get 93 around here, that's all that would go in my car (we don't have 94 that I've seen). Oklahoma sucks for good gas. I get MUCH better gas mileage on 93. I've never even had a tank of less than 91 in my car.

Meg
2007 WRB XT Sport Auto
RocketEyes is offline  
post #3 of 16 (permalink) Old 05-11-2008, 08:33 PM
Registered User
 
satalac's Avatar
 
Join Date: Feb 2008
Location: Nashville
Posts: 1,539
Car Year: 04
Car Model: Forester XT
Gallery: 0
Feedback Score: 0 reviews
use the recommended octane for the car that subaru says. i believe it's 87. please someone correct me if i'm wrong. anything else and you're just wasting money.
satalac is offline  
post #4 of 16 (permalink) Old 05-11-2008, 08:39 PM
Forum Member
 
YoGeorge's Avatar
 
Join Date: Apr 2008
Location: Grosse Pointe Farms, MI
Posts: 1,477
Car Year: 2009
Car Model: Forester
Gallery: 0
Garage
Feedback Score: 0 reviews
87 octane is fine....

Quote:
Originally Posted by lukesforester View Post
Hey i just got my forester, I've heard there 10:1 compression ratio.
To me that seems high so would i get better mpg and or better performance from higher octane gas, 89,91 or even ultra94... i work at sunoco lol
That is what's specified, and going to a higher octane will give you zilch in terms of a performance improvement.

There are *some* cars that will tune for the range between 87 and 91 or 93 octane--my son's '97 BMW 318ti (four cylinder) recommends premium but is completely OK to run on regular or midgrade. I believe that the 6-cylinder Outback is the same--recommends premium, but will run on regular with slightly decreased performance.

But if a car is designed for regular, it's fine on regular. I believe my wife's '07 Honda Civic has a 10.5:1 compression ratio, and regular fuel is all that's required.

If you work at a Sunoco and get gas for free, or if you don't have to pay any more for higher octane, you could run it on 89 or something like that, but you really don't need to.

George
YoGeorge is offline  
post #5 of 16 (permalink) Old 05-11-2008, 08:41 PM
Forum Member
 
wakeabyss's Avatar
 
Join Date: Mar 2007
Location: Boise, Idaho
Posts: 2,885
Car Year: 2005
Car Model: Sequoia, V70R
Transmission: auto
Gallery: 0
Feedback Score: 13 reviews
Quote:
Originally Posted by satalac View Post
use the recommended octane for the car that subaru says. i believe it's 87. please someone correct me if i'm wrong. anything else and you're just wasting money.
For NA foresters I believe the minimum octane rating is 87. I use 93 in my FXT.
wakeabyss is offline  
post #6 of 16 (permalink) Old 05-11-2008, 09:00 PM
The Seventh Sister
Administrator
 
pleiad7's Avatar
 
Join Date: Jan 2006
Location: Sonoma County, CA
Posts: 27,310
Car Year: 2004
Car Model: Forester XT Premium
Transmission: 4EAT
Gallery: 70
Garage
Feedback Score: 50 reviews
Quote:
Originally Posted by satalac View Post
use the recommended octane for the car that subaru says. i believe it's 87. please someone correct me if i'm wrong. anything else and you're just wasting money.
+1

-Silke
04 FXT PP PSM ~ "Subed"
98 Forester S ~ "Slynki"
pleiad7 is offline  
post #7 of 16 (permalink) Old 05-11-2008, 10:24 PM
Registered User
 
satalac's Avatar
 
Join Date: Feb 2008
Location: Nashville
Posts: 1,539
Car Year: 04
Car Model: Forester XT
Gallery: 0
Feedback Score: 0 reviews
Quote:
Originally Posted by wakeabyss View Post
For NA foresters I believe the minimum octane rating is 87. I use 93 in my FXT.
i use 93 in my fxt as well. i don't get the minimum 91 down here. darn .
satalac is offline  
post #8 of 16 (permalink) Old 05-11-2008, 10:51 PM
Forum Member
 
ziggie216's Avatar
 
Join Date: Jul 2007
Location: Bay Area, CA
Posts: 532
Car Year: 07
Car Model: Forester
Gallery: 0
Feedback Score: 0 reviews
If you're putting 91 in your car thats asking for 87, you might as well just paypal me the extra cash you got there.
ziggie216 is offline  
post #9 of 16 (permalink) Old 05-12-2008, 12:28 AM
Forum Member
 
webtoole's Avatar
 
Join Date: May 2008
Location: USA
Posts: 45
Car Year: 09
Car Model: Forester
Gallery: 2
Feedback Score: 0 reviews
New 09 FXT

I asked the dealer about the Octane after reading the forums here. I read that up until the 09, that anything but premium would overheat the engines on 06-08 FXT's, but after talking to the dealer, he said that my 09 FXT recommends premium with a minimum of 91, but that if I ran 87 that I would do no damage to the engine, but would loose about 4 to 6 HP. He said that the XT's are tuned to premium. I use 91 in Arkasnas and it only about 20 cents more per gallon. Anybody use Octane Booster in thier new 08/09's? I have heard to stay away from them, but if anybody knows of one that works or is ok to use on a FXT let us know. Thanks
webtoole is offline  
post #10 of 16 (permalink) Old 05-12-2008, 04:55 AM
Contributing Member
 
ferret's Avatar
 
Join Date: Jan 2006
Location: Northern NJ
Posts: 3,354
Car Year: 2014
Car Model: Impreza Ltd
Transmission: CVT
Gallery: 0
Feedback Score: 6 reviews
I have a N/A 04 5 Speed. On my many travels I logged mileage as well as other services. Since day 1, when I run the recommended 87, I get some octane knock. When I run my OBDII display on the passenger seat right next to me, I see the timing retard when I hear that knock. It goes from 42 BTC to 12 BTC ( at least I know the knock sensor is working ). The best mileage I got from 87 was 30 mpg.

Then on a lark, I tried 'plus' 89 ( .10 more per gallon ) , no more knock and no more retarded timing. My mileage increased and on the highway I consistently get over 30 mpg usually in the 33-34 mpg.

For me, and extra $1 or so at fillup is worth the extra 30 or more miles I get out of a tank of gas, and cheaper.

End of my $.02 and experiences.

98S, 2014 Impreza 5 dr Ltd (9 Subaru's since 1978, 7 were 5 sp) ILuvSubaru's
ferret is offline  
post #11 of 16 (permalink) Old 05-12-2008, 05:34 AM
Forum Member
 
INSubbie's Avatar
 
Join Date: Apr 2008
Location: Saint Louis, Missouri
Posts: 537
Car Year: 2006
Car Model: Forester XT Limited
Transmission: 5 Speed Manual
Gallery: 0
Feedback Score: 1 reviews
There is a lot of posts already on here if you search for "recommended fuel for turbo" or something like that. This seems to always be creeping back in. LOL

Well, just to sum it up, if you have a Subaru with a turbo, it is critical that you use nothing less than 91 octane. If you run for extended periods of time on regular, you will eventually burn up your turbo for starters, which wouldn't be covered under warranty. I don't know why your dealer told you it was just fine to run regular if premium is recommended. Obviously he didn't get the memo! LOL

If you look in your manual, it also says that in an emergency, you can use the regular gas if premium cannot be found. If you do use regular gas, you will be taking a severe hit on performance (and not just HP will be affected!!!) as the knock sensors will pick up on this and have the ECM (Engine Control Module) to adjust the timing to accommodate the lesser fuel.

If your car specifies regular 87 octane, than it will not run any better or get better gas mileage and you will be wasting your money; It will only run hotter. The ECM cannot adjust for this scenario as it was only tuned to run on the regular 87 gas. I have seen some stations in New Mexico, Arizona, and Nevada that sell regular 85 octane and mid grade 87. Just make sure that you are always using the fuel the car manufacture recommends.

EDIT: Octane Boost WILL NOT improve the quality of fuel. It is not a magic wand to fix everything. As an additional not to that, for the cost of premium fuel vs. regular fuel in the tank, the cost to put in the premium would be cheeper than buying the bottle of boost to put in after the fact!

'06 XT w/ 5MT

Last edited by INSubbie; 05-12-2008 at 05:40 AM.
INSubbie is offline  
post #12 of 16 (permalink) Old 05-12-2008, 07:29 AM Thread Starter
Registered User
 
lukesforester's Avatar
 
Join Date: May 2008
Location: verona ont. canada
Posts: 47
Car Year: 1999
Car Model: forester s
Gallery: 0
Feedback Score: 0 reviews
Quote:
Originally Posted by YoGeorge View Post
If you work at a Sunoco and get gas for free, or if you don't have to pay any more for higher octane, you could run it on 89 or something like that, but you really don't need to.

George
LOL I wish
lukesforester is offline  
post #13 of 16 (permalink) Old 05-12-2008, 07:48 AM
Forum Member
 
funkymonkey1002's Avatar
 
Join Date: Jan 2006
Location: Boston
Posts: 9,013
Car Year: 2004
Car Model: 2.5 XT
Transmission: 4eat
Gallery: 0
Feedback Score: 8 reviews
Yea, I wouldn't recommend 99% of octane boosters. The majority of them only bump the fuel up a few octane -points-, not even one full octane.

04xt/4eat, 16g, STI bits and bobs
funkymonkey1002 is offline  
post #14 of 16 (permalink) Old 05-12-2008, 12:28 PM
Forum Member
 
TheEmrys's Avatar
 
Join Date: Oct 2007
Location: Northern Colorado
Posts: 442
Car Year: 1999
Car Model: Forester S w/AT
Gallery: 0
Feedback Score: 0 reviews
Here in Colorado, we have 85/87/91. I use 85 for our Subaru, 87 for our Honda CRX. Compression ratio dictates for that. Our El Camino uses 91.
TheEmrys is offline  
post #15 of 16 (permalink) Old 05-12-2008, 01:10 PM
Registered User
 
satalac's Avatar
 
Join Date: Feb 2008
Location: Nashville
Posts: 1,539
Car Year: 04
Car Model: Forester XT
Gallery: 0
Feedback Score: 0 reviews
Quote:
Originally Posted by TheEmrys View Post
Here in Colorado, we have 85/87/91. I use 85 for our Subaru, 87 for our Honda CRX. Compression ratio dictates for that. Our El Camino uses 91.
well i doubt you bought your el camino for it's great gas mileage .
satalac is offline  
Sponsored Links
Advertisement
 
Reply

  Subaru Forester Owners Forum > Technical Forums and Vehicle Assistance > Engine and Exhaust > EJ25 - 2.5L Non-Turbo (1998-2010)

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Subaru Forester Owners Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools Search this Thread
Show Printable Version Show Printable Version
Email this Page Email this Page
Search this Thread:

Advanced Search
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may 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
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome