87 octane can only be used?

aaandht · Apr 1, 2006

My dad just got a 2006 GT(literally) but he read how it stresses to only use 87 octaine. With his pervious mustang GT's he has put in 93 octaine and can't seem to understand why they are stressing it so much to use only 87. Anyone have some insight on this, performance gains/reliablity problems using anything other than 87?

Thanks

Humboldt Stang · Apr 1, 2006

The car comes tuned for 87, and unless you modify your car, there is no need for higher octane.
Can you put higher octane in? Yes.
Will it harm your car? No.
Will it do anything except waste money? No.

bigcat · Apr 1, 2006

GOLDENPONY · Apr 1, 2006

Octane?

Actually, I read the engine is tuned for preimum but the knock sensors allow you to use 87 octane. The knock sensors retard the timing, so if you use higher octane fuel, the timing advances and you'll get a LITTLE more HP. I use preimum and the car runs great-do not believe the people that say higher octane will damage your engine because this is not true. If the knock sensor story isn't true, the worst thing is you spend a little more to fill up, but you'll also keep your fuel system and your whole engine cleaner.

FLY2kGT · Apr 2, 2006

LOL...here it is again. Does anybody ever google a question and look it up for themselves? I'm not going to answer again, as a quick search on this board will reveal the answer. I'd like to know where you read the engine was tuned for premium, because they forgot to tell the Ford engineers to change their recommendation in the owner's manual. As for higher octane containing more cleaning agents, where in the world did that come from? I'm done before I really get on a rant.

JRPony · Apr 3, 2006

GOLDENPONY said:
Actually, I read the engine is tuned for preimum but the knock sensors allow you to use 87 octane. The knock sensors retard the timing, so if you use higher octane fuel, the timing advances and you'll get a LITTLE more HP. I use preimum and the car runs great-do not believe the people that say higher octane will damage your engine because this is not true. If the knock sensor story isn't true, the worst thing is you spend a little more to fill up, but you'll also keep your fuel system and your whole engine cleaner.

This post is 100% incorrect.

Adam2004 · Apr 3, 2006

GOLDENPONY said:
Actually, I read the engine is tuned for preimum but the knock sensors allow you to use 87 octane. The knock sensors retard the timing, so if you use higher octane fuel, the timing advances and you'll get a LITTLE more HP. I use preimum and the car runs great-do not believe the people that say higher octane will damage your engine because this is not true. If the knock sensor story isn't true, the worst thing is you spend a little more to fill up, but you'll also keep your fuel system and your whole engine cleaner.

Noob alert

GOLDENPONY · Apr 4, 2006

Fuel

JRPony said:
This post is 100% incorrect.

You're entitled to your opinion.

Randyp · Apr 4, 2006

5.0 Mustang magazine tested this about a year ago on a bone stock '05 GT.
93 octane gas allowed the computer to advance the timing with the end result being a 5 RWHP increase over running 87 octane gas. Really not worth running 93 octane until needed for that blower,etc.

rich8566 · Apr 4, 2006

Randyp said:
5.0 Mustang magazine tested this about a year ago on a bone stock '05 GT.
93 octane gas allowed the computer to advance the timing with the end result being a 5 RWHP increase over running 87 octane gas. Really not worth running 93 octane until needed for that blower,etc.

My car does not run well on 87 octane. I use 89 now and the car runs much better. I was getting slight pinging on 87 and the 89 has cleared that up.

MATRIX4.6 · Apr 5, 2006

My salesman told me that running 91 octane and that with my black paint I should see around a bigillion more horsepower...I have also read on the net that black is the fastest color...this is 100 percent biblical.period.

FLY2kGT · Apr 5, 2006

Just curious here, but perhaps one of you with the endless knowledge can tell me EXACTLY how the vehicle computer KNOWS what octane fuel is in the TANK so that it may ALLOW THE COMPUTER TO ADVANCE THE TIMING? Did somebody sneak in and install some sort of fuel octane sensor without my knowledge?

RickInIndy · Apr 5, 2006

Its not that the car knows the octane, it just knows if it's getting knock through a knock sensor. If it detects this it will retard timing. The computer can only retard the timing so far though. I'll qualify this by saying I have no clue about how this works in a Mustang but that is the way it worked on my 86 GN. With the turbo, it was a lot more critical to monitor knock. Head gaskets are the weakest link!!

I guess the question here is does the mustang have a knock sensor that retards timing with lower octane fuel? If so then it would have higher timing for higher octane which would seem to improve power. Just a thought from another noob.

jlisle01 · Apr 5, 2006

The car does come tuned for premium. The knock sensor retards timing when it detects knocking as knock sensors have for decades now (hence the name "knock sensor". Why is that so hard to understand? P.S. For you guys who know their Ford history, black really is (or at least was) the fastest color. That's why the Model T was only available in black. Old man Ford had a study done to determine the color paint that dried the fastest and black was it.

FLY2kGT · Apr 5, 2006

So, let me get this straight. The car comes tuned for PREMIUM, but the manual tells you to put 87 octane in it so the engine will knock on purpose, therefore telling the computer to retard the timing so that the engine runs properly? Or are you telling me that the computer advances the timing until knock is detected and then the timing is retarded to the proper degree? I'm no rocket scientist, nor do I claim to be, but what I have seen in this thread makes no sense.

Humboldt Stang · Apr 6, 2006

DukeOfValencia · Apr 6, 2006

so what is the difference between the aftermarket 87 tune and the 91 tune? If the engine automatically adjusts timing according to the knock sensor, why would there be a different tune for different octane ratings?

RickInIndy · Apr 6, 2006

I would have to guess that the computer in the Mustang is set to run a given timing, stock, unless it detects knock. Then it will retard timing. I would guess the aftermarket tunes set this timing level higher to take advantage of the higher octane. The knock sensor will still retard timing if knock is detected.

So that being said, if a stock mustang is running 87 octane and is detecting no knock, it will be running at the same timing as if it had higher octane.

But, if you are running 87 octane and it is detecting knock, it will run faster on higher octane fuel.

So unless you know if the timing is being retarded running 87 octane with a factory tune you will not know if it will do better with a higher octane. Heat probably plays a factor in this also.

Don't bake me, I did say I was a noob!!!!

Is there a software program yet that will monitor and display the computer readings? I had that with the GN and you could actually play back a run and see how much knock was detected, air fuel mixtures and a bunch of cool stuff.

Msb · Dec 24, 2018

So I bought my first mustang. An 06 GT. Used of course. I ran regular gas at first. And it started missing. Changed all spark plugs and a coil packs. Fixed the missing problem. But I’d still all ways have it run rich when I’d get on the throttle. Switched over to premium fuel and it’s been running great ever since. Reading all these forums I’m just guessing the dude before me had a time on it. Any guesses?

Dino Dino Bambino · Dec 25, 2018

The '05-'09 GT is tuned conservatively from the factory to run on 87 octane fuel and doesn't have adaptive spark to advance the timing if you run higher octane fuel, so there's little benefit in running higher octane fuel on the factory tune. If you want to gain some performance by running higher octane fuel, you'll need to retune the ECU with more aggressive spark timing.
Hope that settles it.

87 octane can only be used?

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