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Old 07-04-2013, 02:40 PM   #1
dared3vil0
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Default 87 Octane question...

Hello all, i'd like to start off by saying a couple things... 1) Yes i searched and all i could find are results related to tuning for a different octane, or GT octane questions. 2) My question is related to a STOCK 14' 3.7.

I didn't see a "premium fuel is recommended/required sticker anywhere, but i have seen a couple people talking on various Mustang forums that the 3.7 isn't really tuned for 87, that it WILL run on it without too much knock, but power and fuel economy suffer greatly. Anyone know if this is true? Is it worth going to 91? Thanks everyone!
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Old 07-04-2013, 03:56 PM   #2
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What is recommended in the manual?
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Old 07-04-2013, 04:05 PM   #3
dared3vil0
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^ It recommends 87, but that wasn't my question. My question was related to power and fuel economy on premium...
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Old 07-04-2013, 05:29 PM   #4
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I realize what you asked....wasting your money with premium unless your car can adapt like the 5.0 in the GT.
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Old 07-04-2013, 05:40 PM   #5
dared3vil0
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Quote:
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I realize what you asked....wasting your money with premium unless your car can adapt like the 5.0 in the GT.
Considering i've owned it for 3 days and haven't needed to fill up yet, i'd wager a bet i haven't wasted a cent. Thanks for playing.
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Old 07-04-2013, 06:29 PM   #6
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Unless the control unit can adapt to higher octane then buying a higher octane fuel won't do anything.

The 5.0 can adapt up to 93 iirc to up the power a bit
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Old 07-04-2013, 06:40 PM   #7
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Quote:
Originally Posted by dared3vil0 View Post
My question is related to a STOCK 14' 3.7.

I didn't see a "premium fuel is recommended/required sticker anywhere.

Because there isn't one.

, but i have seen a couple people talking on various Mustang forums that the 3.7 isn't really tuned for 87, that it WILL run on it without too much knock, but power and fuel economy suffer greatly.

They are idiots.

Anyone know if this is true?

No.

Is it worth going to 91?
No, read your owners manual.
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Old 07-04-2013, 06:58 PM   #8
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As AzPete mentioned, you'll waste your money on higher octane if you're not tuned for it. By virtue of the OM not stating anything about using higher octane (like the OM for the 5.0 does), your 3.7L is tuned for 87 and using a higher octane won't gain you more than a few, if ANY, RWHP. Of course, there's the placebo effect, similar to how much faster my car is after a good cleaning and wax.
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Old 07-04-2013, 07:20 PM   #9
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The computer on the 3.7 will advance timing until knock is detected by the knock sensors. The computer will bump the timing back to stop the knock. Higher octane fuel will not cause knock as soon as a lower octane fuel...will your 3.7 engine benefit from this? Of course it will...can you feel a difference from the drivers seat? Doubtful...

EDIT: when I say benefit, I mean your engine will have less knocking based on the total load you put on it

Last edited by vixr; 07-04-2013 at 07:38 PM.
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Old 07-04-2013, 08:06 PM   #10
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The 3.7 has similar adaptive programming to the 5.0 - we tried it out on the dyno and it picked up some RWHP and torque on the stock tune by using 93. Wasn't big (I can't remember the difference now) but was close to a tune for 93.

The car runs fine on 87 with no problems. Whoever told you that fuel economy suffers on the 87 octane doesn't know what he is talking about. I get the best MPG on the stock tune and 87 octane.
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