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Old 10-26-2011, 06:01 PM   #1 (permalink)
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Default 87 Octane?

Guys,

All my previous cars have taken the high grade 93 octane gas. I understand that Subaru has designed engines forever to run on 87 octane gas.

I am looking forward to this $.25 +/- per gallon when my new 2.5 Outback comes in.

BUT I have a friend that says to put in the 93 octane no mater what the manual says and the engine will last longer and the car will run better.

Any truth to this???? Or does everyone here get along just fine with the low-grade 87 octane gas???

Thanks,

Flagg
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Old 10-26-2011, 06:06 PM   #2 (permalink)
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No truth at all.

Only reason for premium is if the car requires it (like the turbo models or older 3.0 engine) or if the car is pinging/knocking. The 2.5 will do just fine on the 87 it is designed for.
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Old 10-26-2011, 06:11 PM   #3 (permalink)
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butt dyno
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Old 10-26-2011, 06:39 PM   #4 (permalink)
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I run 89 octane in my 3.6. The first few weeks I was putting 93 in it out of habit and owning a SAAB 9-3T and talk about blowing money out the tail pipe....I have also run 87 and it runs alittle smoother.....
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Old 10-26-2011, 06:54 PM   #5 (permalink)
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Quote:
Originally Posted by Flagg View Post
BUT I have a friend that says to put in the 93 octane no mater what the manual says and the engine will last longer and the car will run better.
The only thing that will last longer and run better is the oil company fat cat retirement accounts. Save your money, buy 87.
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Old 10-26-2011, 08:45 PM   #6 (permalink)
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From day one I've used C****o 87 (except one tank at Freddie Meyer, and it was 87 octane), have had no performance problems. One of the reasons I waited until now to even get an OB was the premium gas requirement.
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Old 10-27-2011, 11:31 PM   #7 (permalink)
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Mine has always had stale, lawnmower grade, gas in it too. Lately I've been filling up with a major discount from Kroger and keeping extra cans around since the limit is 20 gallons for the discount and the car usually takes about 15.
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Old 10-28-2011, 07:37 AM   #8 (permalink)
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What I don't get is my last car (toyota sienna) only required 87 octane but the manual clearly stated that if you were going to do some towing or heavy hauling that they then recommended premium fuel. So that engine at least must have had some ability to advance the timing or some such shyte to say that wouldn't it???
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Old 10-29-2011, 02:09 PM   #9 (permalink)
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ALL engines have the ability to adjust timing. Running 87 in a modern turbo will just cause it to delay timing and drop boost, causing poor performance.

As mentioned the octane rating is based on the AKI (anti knock index) for a high compression engine (turbo, high performance) if you use too low octane the fuel can predontanate under compression before the spark is introduced, causing pinging or knocking. That is why higher octane is required.

If the manufacturer designed the engine to run on 87 (as MOST do) then higher octane could actually degrade performance, and it certainly won't help it.

The manufacturers tend to know what they are talking about when they suggest a fuel to use, after all what do they care what you use, they are going to suggest whatever makes their vehicles perform and last best.

You're friend probably also thinks his CAI adds 25hp and his Exhause increased power by 50%
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Old 11-01-2011, 07:36 AM   #10 (permalink)
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Quote:
Originally Posted by vr4Legacy View Post
ALL engines have the ability to adjust timing. Running 87 in a modern turbo will just cause it to delay timing and drop boost, causing poor performance.

As mentioned the octane rating is based on the AKI (anti knock index) for a high compression engine (turbo, high performance) if you use too low octane the fuel can predontanate under compression before the spark is introduced, causing pinging or knocking. That is why higher octane is required.

If the manufacturer designed the engine to run on 87 (as MOST do) then higher octane could actually degrade performance, and it certainly won't help it.

The manufacturers tend to know what they are talking about when they suggest a fuel to use, after all what do they care what you use, they are going to suggest whatever makes their vehicles perform and last best.

You're friend probably also thinks his CAI adds 25hp and his Exhause increased power by 50%
so apparently the engine in my last car was designed to run on high octane but they rated it for 87 knowing the engine would detune itself?
IF they state in the manual to run on high octane for towing that must mean the engine was designed to take advantage of that correct?
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