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104+ Octane Booster

FishGeek

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Didn't see a place in the Technical Section so I'm posting here...

I was under the impression that I SHOULD be using 93 Octane fuel in my completely stock 15 GT but where I live the max available is 91.

I thought I might try an octane booster and just add it to regular 87 octane fuel (actually the blended stuff up to 10% ethanol). So here's how it went down:

I had a little less than half a tank of 91, to which I added the contents of the octane booster and topped off with regular 87 fuel.

Within a days worth of driving, my Avg MPG, as reported by the dashboard info, dropped from 14 to 13.

Driving behavior was unchanged (as much as I can tell).

What are your thoughts on why this might be?

1) Octane booster is a gimmick
2) Mixing 87+91+booster
3) Resulting Octane level too high for the stock tune parameters
4) El Nino
5) Solar Flares
6) Some other mysterious force in the cosmos

Oh...also...the owners manual indicates 87....should I just go with the basic stuff or keep using 91? I know there are tunes available for 91 but I will most likely wait until I have a few mods before I modify the tuning.
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nastang87xx

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Filling with 91. Avoid the headaches. Have peace of mind. Don't believe everything internet warriors tell you. Yay knock sensors!

I've filled up with 91 on my GT350 several times and it INSTANTLY blew up...the driver's ears that were right next to me.

Fill up on 91 and just drive it.
 

Mustang1260

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Average consensus (you will get opinions all over the board)

1. Octane boosters are CRAP
2. Pull your plugs--some boosters discolor and foul plugs
3. Your car runs perfectly fine on 91.
4. Your car runs perfectly fine on 91.
5. Your car runs perfectly fine on 91.
6. Carefully read up on the booster you used-- Most do NOT provide the octane boost people think it does. Really read the label and think it through. They may exist but I have not seen a booster that states: add this to 10 gals of 91 fuel to increase it to 93, 95 etc .... they do not phrase their language that way. Again, carefully read the bottle. And why add it to 89? If your worried about 91 being too low you clearly went in the wrong direction. You had 91 but added 87 which the booster may have taken up to 88. So half a tank of 91 and half a tank of 88 = 89.5. You were better off just adding 91.

What 'brand' of boost did you use and how many cans did you add to the tank?
I've seen some advertise they increase Octane by 2% per 8 gallons...so if it all worked properly that 87 would increase by 2% to: 88.74%. Big whop.
 

NvrFinished

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I live in California and all we have is 91 octane. I run my car hard at various road courses. You will be fine.
 

nastang87xx

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Also filling up on 87 on a Coyote pulls back timing and loses a whole peak of about 15 HP. This is WOT mind you too. You'll never feel that in every day driving. However, fill up premium anyway for the other added benefits such as detergents.
 

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FishGeek

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Average consensus (you will get opinions all over the board)

1. Octane boosters are CRAP
2. Pull your plugs--some boosters discolor and foul plugs
3. Your car runs perfectly fine on 91.
4. Your car runs perfectly fine on 91.
5. Your car runs perfectly fine on 91.
6. Carefully read up on the booster you used-- Most do NOT provide the octane boost people think it does. Really read the label and think it through. They may exist but I have not seen a booster that states: add this to 10 gals of 91 fuel to increase it to 93, 95 etc .... they do not phrase their language that way. Again, carefully read the bottle. And why add it to 89? If your worried about 91 being too low you clearly went in the wrong direction. You had 91 but added 87 which the booster may have taken up to 88. So half a tank of 91 and half a tank of 88 = 89.5. You were better off just adding 91.

What 'brand' of boost did you use and how many cans did you add to the tank?
I've seen some advertise they increase Octane by 2% per 8 gallons...so if it all worked properly that 87 would increase by 2% to: 88.74%. Big whop.

So the idea was that WITH the boost I could use a lower octane fuel..
The brand name was 104+
The rest of your explanation makes alot of sense. None of the available products provide details. The most detail they have is "Treats up to X Gal," in the case of the bottle I used it was 25 gallons. I suspect that even if this is "one of the good one" the reality is that it probably didn't raise it much....and mixing a lower octane+whatever the booster gave me may well have resulted in something less than 91.

Given the cost of the booster...I am financially better off just putting in 91 and calling it a day.

I'll run this fuel out and refill with 91 and see what happens.
 

jasonstang

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91 is more than enough for factory tune. You are not gonna bet better with octane booster.
Who said you should be using 93?
 
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FishGeek

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I was looking for this information and I couldn't find it.

Good digging.
I was about to say the same thing....the write up for 104+ indicated that it couldn't be definitively claimed to raise your octane to any particular level.
 

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FishGeek

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There is one station here in town that sell actual gasoline with no ethanol....

I'm thinking that I might fill up with that stuff next time and run a few unscientific tests to see what my avg mpg is after using that and the other ethanol blend.

With all the advanced ignition controls in modern vehicles, it may not make a spit of difference though.
 

WildHorse

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Houston Kid

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Give Torco a try. Expensive to run everyday, but run a tank or two and see what your butt dyno tells you. It has specific mixing instructions to achieve different octane levels.

I've run a few tanks in the GT350 and put it on the dyno. Best guess the mixture I ran was around 100 octane. 489 at the wheels SAE corrected. I need to run a dyno on 93 to see what gain was actually had. We have 93 here. No other mods. The 5.2 will adjust quite a bit for higher octane fuel.
 

Austinj427

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The problem with Torco is it turns your plugs orange, which could cause questions if you ever had a warranty issue.
 

Trackaholic

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I'm in CA where our best widely available is 91. No problem with the GT350.

I'd run 93 if we had it but since we don't I just use 91.

You will lose a little fuel economy with oxygenated fuel, as the 10% ethanol has less energy than the 10% gasoline it replaces. If you normally run 100% gas, that might explain the MPG drop. Or it could just be statistical variation.

-T
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