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2.5 Premium or regular gas


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8 replies to this topic

#1 FSRBIKER

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Posted 09 April 2008 - 04:36 PM

I installed a 96 2.5 in my 97 Legacy Outback and I have been using regular not premium gas, can I expect a big bump in power and mileage if I do use Super?

I am knocking on wood when I say this but she runs fine on regular but a 2-3 mpg bump and more power would make me switch.

#2 screwbaru2

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Posted 09 April 2008 - 05:23 PM

According from what I've read on this site the 96 requires premium.

#3 mdjdc

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Posted 09 April 2008 - 05:38 PM

The 96 has different pistons and therefore a higher compression ratio. It requires premium fuel in order to keep it running properly. Right now you are depending on the knock sensor to keep it from pinging by retarding the timing. Eventually you will run into problems. This is precosely the reason I replaced the 96 engine with a 98 in my wifes 96 outback.

I know premium is much more expensive, but in the long run you will save on engine replacement.

#4 FSRBIKER

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Posted 09 April 2008 - 06:42 PM

I am assuming I have a 96 engine since it has hydraulic lifters, it was a replacement engine from Japan. Any other way to tell?

The 96 has different pistons and therefore a higher compression ratio. It requires premium fuel in order to keep it running properly. Right now you are depending on the knock sensor to keep it from pinging by retarding the timing. Eventually you will run into problems. This is precosely the reason I replaced the 96 engine with a 98 in my wifes 96 outback.

I know premium is much more expensive, but in the long run you will save on engine replacement.



#5 PAezb

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Posted 09 April 2008 - 07:43 PM

The 96 owners manual states 91 Octane is recommended, but 87 can be used.
For the 12+ years I have owned my 96 OBW (237K). I normally put 87 in it, occassionally 89, and 91 when towing. I can't tell much if there is a increase in power at 91 but would probably say it seems to run best on 89.

I wouldn't worry too much about it.

Oh, and yes the 96 2.5 has hydraulic lifters....

#6 grossgary

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Posted 10 April 2008 - 12:11 AM

I am assuming I have a 96 engine since it has hydraulic lifters, it was a replacement engine from Japan. Any other way to tell?

96 also has a bracket above the timing belt at the crank that was installed just for delivery purposes...which means it could be removed to, but if you have it that's a 1996 only deal.

#7 FSRBIKER

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Posted 10 April 2008 - 07:45 AM

96 also has a bracket above the timing belt at the crank that was installed just for delivery purposes...which means it could be removed to, but if you have it that's a 1996 only deal.


So that's underneath the plastic cover then right? No other marking/numbers on the block/heads? I am going to get my brother's MAC Taskmaster Scan tool and watch and see if I can tell that the timing is getting retarded at any RPM. If it does then I'll have to fill up with Super and try it again.

#8 grossgary

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Posted 10 April 2008 - 07:49 AM

yes that will be noticeable under the center timing cover.

#9 Bluestone

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Posted 10 April 2008 - 08:53 AM

Back in the days of pre-unleaded gas, premium grade gas was as high as 98-100 octane, mid-range 95-97 and regular 92-94.
Now, the unleaded pisswater;) which passes for gasoline ranges from 87 octane for regular to 91 octane for premium(:lol:), and at $4 per gallon and rising. And our cars come equipped with complicated and costly electronics to allow the engine to run efficiently on the anemic swill.
Anyway, I've always used mid-range gas, 89 octane in my Sube even though it's designed to run on a minimum of 87. I just feel that's it's better for the engine in the long run.
My Subie's engine never pings under hard acceleration. Only if I start up from a dead stop on a reasonably steep hill will I get a slight ping initially, and then only for less than a second.
Paying the 10 cents a gallon more for a bit higher octane gas really doesn't add that much to one's overall yearly car maintenance expenses, especially when compared to all the other costs associated with car ownership.
And a steady diet of a couple of extra octane, especially in these days of extra low calorie gas, is likely kinder to the engine.




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