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Discussion Starter #1
With fuel prices so high I wanted to know if it really matters what type of fuel I get for my 2004 automatic 3.9L Mustang. I don't have ANY engine mods yet, but got my ebay CAI on the road...hope to get it this Thursday.

My friend can beat by a hair w/ his Suburban that has a Vortec 320-something I think (100% stock)...and was wondering if he can beat me by just a little on 87 grade will I run any faster on 91? We drag race from complete stop to an estimated 1/4 mile.

Also how much faster should I expect to run w/ my CAI installed?
 

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Discussion Starter #3
So you're saying I'm gonna run slower w/ CAI? Why would I run slower? Is there any benefit to usinger better grade fuel?
 

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megax29 said:
So you're saying I'm gonna run slower w/ CAI? Why would I run slower? Is there any benefit to usinger better grade fuel?
No youll drop your time a little bit, so youd be going quicker. You don't gain anything from using a higher octane unless your computer is tuned for it. So if you were to, for example, advance your timing you would have to run 93 octane.
 

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Discussion Starter #5
No youll drop your time a little bit, so youd be going quicker. You don't gain anything from using a higher octane unless your computer is tuned for it. So if you were to, for example, advance your timing you would have to run 93 octane.
Don't you contradict yourself by saying I'll drop my time a bit so I'd be going quicker. How is it possible to be going quicker and manage to run a slower 1/4 mile?

About fuel grade, will I run faster w/ 91 vs 87 w/o any tuning?
 

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you would actually foul your spark plugs faster if you're not tuned for the extra octane and the timing isnt advanced
 

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megax29 said:
Don't you contradict yourself by saying I'll drop my time a bit so I'd be going quicker. How is it possible to be going quicker and manage to run a slower 1/4 mile?

About fuel grade, will I run faster w/ 91 vs 87 w/o any tuning?
What im trying to say is you will run a slightly lower time, meaning that you went down the track in a less amount of time.understand:confused:
 

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Discussion Starter #8
Ah, so I'll go faster decreasing my 1/4 mile time by .1 second, right?
 

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Discussion Starter #10
So what benefit do you gain from paying an extra 20 cents for premium fuel? and what's the purpose for octance boosters
 

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so you mean I should run 87?... I've been running 89-89.5 octane since I got the car... DAMN IT, I could've been saving 2 cents a gallon.... for 30,000 miles... son of a yeah...
 

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running higher octane on non advanced timing does you actually no good.
 

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can I get a chip burnt for 89.5 octane? I never seen 93 around here.... possibly 91, but it's 20 cents higher, and I don't want that.... but 89.5 octane is VERY easy to get, and cheapest in my hometown.... 87 is a little cheaper where I go to school
 

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jimmy_beaner said:
can I get a chip burnt for 89.5 octane? I never seen 93 around here.... possibly 91, but it's 20 cents higher, and I don't want that.... but 89.5 octane is VERY easy to get, and cheapest in my hometown.... 87 is a little cheaper where I go to school
You wont see a difference in performance between 87 and 89.5.. you wont be able to advance the timing enought o matter
 

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So what benefit do you gain from paying an extra 20 cents for premium fuel? and what's the purpose for octance boosters
on a stock mustang, none. the point of higher octane is that it prevents detonation in the engine. Detonation can occur when you are forcing more air in the engine than it is sucking. Also, if you start to lean out having a lower octane will cause detonation. Naturally Aspirated cars that run high compression or forced induction cars will need higher octane. Also more expensive cars (bmw, mercedes, rolls royce, vette, etc) will always run premium because their engines are tuned to run 93 to provide optimum hp without sacrificing lopey idle from wilder cams or etc.

Octane boosters or race gas is for cars that need to raise their octane for times when they can raise their boost levels or race cars that run really high compression to where they need race gas (104-117.5 octane) to prevent detonation. Octane boosters only raise your octane by 0.1 octane instead of full octanes. So if it advertises raises 3 levels, then it raises it from 87 to 87.3. waste of money.

plainly put... you don't need any of those. Just stick with 87 octane and don't worry about the rest.
 

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monkey dont you HAVE to use 93 octane? that sucks how much is gas up there it 171 181 and 191 down here.
 

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Discussion Starter #18
Great explanation monkey thanks a lot.
 

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yea, i have to use 93. it is about 1.86-1.92/gal here for premium
 
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