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What Octane number do you use inyour gas tank?

  • 91-93, Yea Baby!!

    Votes: 111 36.5%
  • 89, does the job, no complaints.

    Votes: 64 21.1%
  • 87, I'm poor, only wish i could use the high stuff.

    Votes: 129 42.4%

  • Total voters
    304
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Discussion Starter #21
No, i dont have a ProECM. I drive alot during the week and fill up about 2 times a week (thank God for Shell gas cards). I used the 87 Octane for 1 month, watched my milage. Then used 89 Octane for 1 month, watched milage. Then use 91 octane now for 6 months. heres the results:

87 Octane, full tank, $22, filled up 2.5 times a week(M-S) =
344 miles

89 Octane, full tank, $23.50, filled up 2 times a week (M-S) =
387 miles

91 Octane, full tank, $24.75, fill up 1 time a week (M-S) =
443 miles

I always fill up on Monday Morning on my way to work. On my drive i do lots of different driving: Up hill, Down hill, lots of curve and corners both up and down, straight aways, speeds from 35-70 MPH.
When people first look at the gas price they dont see the difference it will make in the long run in $. But, gas prices are going up, so i do use the 89 Octane occasionally. but over all, USE THE BETTER OCTANE.
 

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I ran 87 for 6 months i had my car..... switched to 91 maybe 4 months ago and mileage went up 50+ mpg.... ill spend the extra change im sure its just sitting at home in a jar or in my center console
 

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76 Gas ONLY. 89 octane. I tried 91 for several months and determined it runs just as good if not better with 89.
 

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Lower octane also ignites easier thus ensuring a better burn. If your running an na car, you want the lowest octane you can get wihtout knock/ping.
 

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Discussion Starter #28
liigod said:
Lower octane also ignites easier thus ensuring a better burn. If your running an na car, you want the lowest octane you can get wihtout knock/ping.
You forgot to mention the part about the Lower octane doesnt burn as clean as a higher Octane fuel, thus is the cause of most Cat Inefficency CEL. And we all hate that CEL......blinky. haha
 

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91 Honda Accord LX
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824 Posts
the manual says 87. higher octane fuel should only be used for a carburated (non-fuel injected...ie. old) or tuned vehicle.
 

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People, not sure how many times this has been explained or how many times I have read about this but the biggest myth out there is: higher octane equals better gas. This is simply not true. Higher octane only prevents knock, THAT'S IT. It burns slower and requires more spark to ignite. Whoever said that lower octane gas does not burn as clean as high octane is full of crap. This has everything to do with the brand. Crappy gas with 93 octane will leave as many deposits as 87, if not more since it might not burn up completely. Bottom line is that you should use what the manual tells you to. If you do some reading on this subject in professional literature, the rule of thumb is to use the lowest octane that you can get away with, without generating knock. This will assure max performance level. For those who mentioned better gas milage, this might be due to the slower rate of burn, but this will hurt your performance. Make sure that the 87 that gave you bad gas milage was not a crappy brand. Personally, I tried several brands and I literally see a world of difference between them when driving, all being 87. I like Exxon myself. And yes, I did also experiment with 93 octane knowing that it will not do anything for me and it didn't. Once I get proECM chip, I will try 89 and if I get no knock, I will go down to 87 and have a bottle of octane boost ready incase it won't like it. After all of this said, I definitely say 87 for performance unless you hear knock.
 

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09 Legacy spec.B + 01 2.5RS
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I run 89 always in the winter, and either 87 or 89 in the summer.

Why? I ran 87 at first just because it was what was recommended. I read some stuff somewhere, figured it was voodoo, but was like wth i'll run some 89 for a while just to see what happens.

What I see:

I lose a little torque, probably some power. It's not really noticable in feel or anything, but I notice it when watching the spedo/tach just in how long it takes sometimes. Could be wrong, but that seems to be what happens.

Anyhow, that said, I do see an improvement in mileage running 89 instead of 87. And in the winter, the engine sounds a ton 'healthier' on the 89. In the winter on a cold start with 87 it sounds god awful, and I run the 89 just for my own preference.

Very well could just be my head, but I do switch back and forth for a few tanks every now and then just to check myself.

Seems to be holding true so far.

For those who say octane makes no difference on an NA car, that's ridiculous. Knock and detonation happen on NA too, it's just usually less serious due to the pressures. Our engines are fairly high compression though, so avoiding some detonation is never a bad thing.

That said, your car will run happily forever on 87. You probably actually get a bit more power out of it too.

Chances are though, you get a little less mileage (and i'm talking like 10-20 less miles a tank here, so don't read too much into that).

These are my observations, and are very likely to be wrong, feel free to ignore, and your mileage may vary :p
 

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Sunoco 93, unless I can't find a sunoco. I'll try to find a shell or mobil if that's the case. I have to run the good stuff though, due to being turbo.

When I had my RS I ran 87.
 

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Discussion Starter #35
Zioggymama.....ZiggyMammas boy, Your full of crap. What you said made no sense. You said higher octane doesnt burn better, but then the next sentence you say lower octane doesnt burn as good as higher octane. One tank of 93 octane doesnt meen you "experimented", it just meens you didnt wanna take the time to use 6-8 tank fulls of high octane....How many times do I have to say this.....ONE TANK FULL isnt "TRYING" or "Experimenting"! In case you dont know, Subarus run hotter then other cars. Hence the reason why CERTIFIED machanics, Yes, CERTIFIED..means they went to school for this stuff...tells Subaru owners to use higher octane, because our cars run hot and can and will burn higher octane better and cleaner. The SAE and the API (they're engineers so what could they possibly know that a bunch of amateur garage mechanics don't? ) have commissioned tests on "the effect of octane on knock-sensor equipped vehicles". The SAE sells a 109 page book by that same title if you're interested in all the details.

The results of dyno testing acceleration in controlled and well documented conditions with test fleet of regular street cars like a Camry, a Dodge Intrepid and a Blazer showed that over 60% of the cars did better with 89 and 93 octane pump gas than 87.

The MY00 2.5RS owners manual says use 87 or higher.

Ahhh, Im tired of this arguing...cant we all just be RS Friends!
 

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00RS 04STI
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I've run 87-91 and the 91 was an improvement but the .80 increase in gas squashed that so I'm back to 87. I'll try some 91 if the price is right while on my road trip.
 

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91 Honda Accord LX
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CWC.02 said:

Ahhh, Im tired of this arguing...cant we all just be RS Friends!
if ziggy was arguing at all, it would have been founded. but you were really the only one arguing...against the truth, no less.:rolleyes:
 

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As far as the 93 experiment, I do not recall mentioning anywhere 1 tank of gas so, CWC, I don't know where you got that. I did use it for more like 5 months so I do have a good point of reference. In the end, if you feel that higher octane is better, go nuts. It is your car in the end but my point was that there is no technical reason for 93 in the RS. Oh, and by the way, Subaru's do not run THAT hot. 10:1 compression ratio is about average now for N/A. If you're having heat problems, it might be a sing of something else, like old or improper spark plugs.
 
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