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4.6L General Discussion This section is for non-tech specific information pertaining to 4.6L (Modular) Mustangs built from 1996 to 2004.

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Old 10-30-2014, 10:01 PM   #1
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Default What's your thoughts on premium gas

Drive a 2002 gt v8 4.6l only mods I have are catback exaust bbk Cai and bbk throttle body. Would it be a waste of my money to put premium gas in the tank even though it doesn't call for it? Heard a lot of mixed opinions
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Old 10-30-2014, 11:22 PM   #2
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If the car isn't tuned for the extra octane then stick with 87...unless you hear spark knock or some ****in **** ****.
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Old 10-31-2014, 03:25 PM   #3
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^^^ This.

You only need to run premium fuel if your engine is tuned for it.

It may seem counterintuitive, but higher octane fuel actually burns slower. Engines that are tuned for more spark advance utilize this. See the spark plug actually fires slightly before TDC. That way just after TDC the "explosion" has already started and there is maximum pressure in the cylinder to push the piston down (making maximum power). To start this spark earlier (advance the timing) you need the fuel to burn slightly slower so the maximum pressure doesn't occur before TDC. Otherwise you have a piston trying to compress an exponentially increasing pressure which equals broken parts or a "knock" at the minimum.

Higher octane fuel does put out slightly more energy when it burns. However, as previously stated it burns slower. So if you run higher octane fuel on the stock tune, all you're doing is placing your maximum pressure even further away from TDC (potentially slightly reducing power output).

So in short. If you're running the stock tune, run 87 octane. If you're running an aftermarket tune, run whatever it calls for and NEVER anything lower (see broken parts explanation).

EDIT: TDC= Top Dead Center

Last edited by unitedwestang; 10-31-2014 at 03:35 PM.
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Old 10-31-2014, 03:27 PM   #4
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Additionally, though, with the mods you've listed, you may want to consider getting a tune to make the most of what you've got. Bama tunes through Americanmuscle would be perfect for what you have. And its free tunes for life with them if you buy your tuner from them. So if you add anymore mods you just email them and they send you a revised tune.

Last edited by unitedwestang; 10-31-2014 at 03:29 PM.
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Old 11-01-2014, 06:54 AM   #5
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I run premium in mine as I have a canned race tune I run. I would say that I'm fortunate to have an ethanol free station so I get 100% gas so it does allow me to play with the settings.

We the adulterated fuels they vary in alky content from station to station. And with that messing around the the settings would be more difficult. I need to get off my *** and get a dyno tune but for now I believe I have it the best I can get till then.
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Old 11-01-2014, 07:19 AM   #6
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I enjoy my 93 SCT "canned" tune which works well and good mileage, 29-32 mpg hwy. I want a MPT 91 performance tune. Maybe for Christmas!
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Old 11-02-2014, 11:11 AM   #7
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If its not tuned for it, your wasting money just run the 87
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Old 11-05-2014, 07:57 AM   #8
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i run diesel so i can shut my spark plugs off and save electricity
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Old 11-06-2014, 03:44 AM   #9
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Originally Posted by WhiteFoxGT View Post
i run diesel so i can shut my spark plugs off and save electricity

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Old 11-20-2014, 04:51 AM   #10
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There is a lot of misinformation out there, lots of 'myths' about 'myths' almost makes ya think lies are spread by mechanics so they get more business, but from what I've seen my cars run much better on 89 octane. I won't even get into the fuel system cleaner deal (if you don't believe they help, just take out a spark plug and use a scope to take a pic before and after.)

Also I have noticed many of the people who say "there's not benefit to higher octane" usually run higher octane on their own stock 87 vehicles. Kinda like those parents who tell other people's children "oh community college is just fine" but practically murder others to make sure their own kids get into good colleges. I hate people and society so much.
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Last edited by RenGen; 11-20-2014 at 05:05 AM.
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Old 11-20-2014, 04:51 AM
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