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Old 07-14-2011, 10:33 PM   #1
SERENITY_NOW
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Default 93 octane w/10% ethanol or 91 octane ethanol free?

Post asks it all. You opinions and experiences please, as I have access to both here in Vermont.
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Old 07-14-2011, 10:41 PM   #2
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I have been looking for similar answers. My choice is 94 with 10% or 91 without. I've read all the threads on this and still really don't know which would be better for my car.
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Old 07-14-2011, 11:30 PM   #3
MisterMidlifeCrisis
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My 2011 with LS3 runs better on 91 octane without ethanol (my only other choice is 91/92 with ethanol).

The good: fuel economy is up about 10%, seems to have more power, sulfur smell is gone (I tried all of the top tier gasolines before trying non-ethanol and had a sulfur smell with all of them under hard acceleration).

The bad: startup is much louder before NPP valves close (the neighbors even commented on it), there's a bit more cam lope at idle, there's only one gas station selling non-ethanol gas within 15 miles.
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Old 07-14-2011, 11:39 PM   #4
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Originally Posted by SERENITY_NOW View Post
Post asks it all. You opinions and experiences please, as I have access to both here in Vermont.
Depends somewhat on your car. If your owners manual says to run 91 then all you need is 91 and the ethanol free 91 would be even better as each oz of fuel would contain more energy. You would not gain any additional performance using 93 octane and the 10% ethanol would cost you some gas mileage.

If your car requires 91, but recommends 93, as my Z06 does then I would a say it's a trade off.

I'm fortunate, as I can get 94 octane ethanol free gas in my hometown, so I get the maximum performance and the maximum gas mileage. I do pay an additional 10 cents a gallon for the 94 octane ethanol free over 91 octane ethanol free gas. I cut out two nights a year eating at the Golden Corral ($20 total) to pay for the extra cost of the 94 octane.
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Old 07-15-2011, 12:15 AM   #5
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Here's the story. Ethanol contains about 80,000 btu's of energy. Gasoline contains 118,000 btu's of energy. Contrary to popular belief, higher octane does not equate to more power or more energy contained in a gallon of gas. Octane inhibits gasolines ability to burn. Higher octane gas is better suited for higher compression engines prone to detonation. The engine in your C6 is designed for 91 octane gas. This is covered in your owners manual. Since ethanol contains less energy per gallon, you have to add more gas to do the same amount of work. Bottom line, if you burn gas with no ethanol, you will see 5-8% better fuel economy (less gas burned to do the same amount of work) and about a 3-5% increase in horsepower. Yes, gas with ethanol is usually cheaper in most parts of the country. This is because ethanol is subsidised by the government and costs less per gallon. This encourages stations to purchase it because they can sell their gas for less. In some states and locals, it is mandated, usually at 10%. You bought a Corvette for it's performance. Use gas without ethanol and you will feel the difference and get better gas mileage. If you put a pencil to it, you will get enough of an increase in fuel economy to pay the difference in the cost. I could go on for an hour about oxygenated fuel (ethanol) and the effect it has on oxygen sensors but will save that for another discussion. Enjoy!
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Old 07-15-2011, 01:13 AM   #6
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Quote:
Originally Posted by 1Corvette View Post
Here's the story. Ethanol contains about 80,000 btu's of energy. Gasoline contains 118,000 btu's of energy. Contrary to popular belief, higher octane does not equate to more power or more energy contained in a gallon of gas. Octane inhibits gasolines ability to burn. Higher octane gas is better suited for higher compression engines prone to detonation. The engine in your C6 is designed for 91 octane gas. This is covered in your owners manual. Since ethanol contains less energy per gallon, you have to add more gas to do the same amount of work. Bottom line, if you burn gas with no ethanol, you will see 5-8% better fuel economy (less gas burned to do the same amount of work) and about a 3-5% increase in horsepower. Yes, gas with ethanol is usually cheaper in most parts of the country. This is because ethanol is subsidised by the government and costs less per gallon. This encourages stations to purchase it because they can sell their gas for less. In some states and locals, it is mandated, usually at 10%. You bought a Corvette for it's performance. Use gas without ethanol and you will feel the difference and get better gas mileage. If you put a pencil to it, you will get enough of an increase in fuel economy to pay the difference in the cost. I could go on for an hour about oxygenated fuel (ethanol) and the effect it has on oxygen sensors but will save that for another discussion. Enjoy!
And I hate subsidising stuff, especially with negative benefits.
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Old 07-15-2011, 05:49 AM   #7
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No car running the stock tune has optimum power or economy regardless of whats in the tank.
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Old 07-15-2011, 07:05 AM   #8
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Oxygenated fuel ( read 10% EtOH ) with a proper tune will run better.
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Old 07-15-2011, 02:56 PM   #9
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I wish i could get 100 Ethanol! I hate that they put 15% gas in my E85

I let the WHP gain speak for it's self
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Old 07-15-2011, 04:50 PM   #10
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Quote:
Originally Posted by SpinMonster View Post
No car running the stock tune has optimum power or economy regardless of whats in the tank.
Pretty sure the discussion related only to the differences in fuel. If it's more than the fuel, then I could easily upstage your comment with "No car running the stock engine components has optimum power or economy regardless of the tune".
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Old 07-15-2011, 06:24 PM   #11
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The real question would be, are you stock? If so, it doesn't really matter, unlikely you'll see any fuel economy difference, as it's only 10% Ethanol, you'll make the same horsepower.

If you're not stock, and have a tune, run what your tuner tuned your car for or higher only.
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Old 07-15-2011, 06:38 PM   #12
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Originally Posted by res0n0xg View Post
The real question would be, are you stock? If so, it doesn't really matter, unlikely you'll see any fuel economy difference, as it's only 10% Ethanol, you'll make the same horsepower.

If you're not stock, and have a tune, run what your tuner tuned your car for or higher only.
Actually, it does matter. The factory 91 tune is using a stoic value for fuel that is based on 100 % gas, with no exception to the 10 % ethanol blend. This alters the "real" AFR slightly as well because of this stoic fuel difference. 100% pure gas has more power potential per volume than E10 so given the same injector flow you'll have more power and fuel economy with the 100 % gas product.

IMHO, a stock tuned car should make more power and get better fuel economy running straight gasoline as long as there's no KR
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Old 07-15-2011, 06:49 PM   #13
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I know ethanol is a killer on small engines,boats,atvs anything that sets for a period of time that stuff turns to a powder like substance and clogs everything up.So if your car sets for long periods of time wouldnt be good ideal to run it.Just my 2%
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Old 07-15-2011, 09:23 PM   #14
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Without a doubt, 91 octane no ethanol.
Producing ethanol from corn is a net energy looser and no one except a BS politician
would advocate doing it if they really cared about energy consumption and the economy.
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Old 07-16-2011, 01:14 PM   #15
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Quote:
Originally Posted by SERENITY_NOW View Post
Post asks it all. You opinions and experiences please, as I have access to both here in Vermont.
Here is another way to look at it. The 91 octane and the 93 octane E10 are the exact same 91 octane fuel. By adding 10% ethanol, which has an octane rating of 113, to the 91 octane, it brought the octane rating up to 93. ((91 x 9) + 113)) / 10 = 93.2

So basically by buying the 93 E10 you are paying around 10 - 12 cents per gallon more for 90% of a lower grade fuel that has been cut with 10% of a product that will cut your fuel mileage by 2 -3 miles per gallon.
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Old 07-16-2011, 09:19 PM   #16
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Quote:
Originally Posted by LS3_E85_Corvette View Post
I wish i could get 100 Ethanol! I hate that they put 15% gas in my E85

I let the WHP gain speak for it's self
100% EtOH will help with HP but suck for fuel milage
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Old 07-20-2011, 08:49 PM   #17
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Originally Posted by AU N EGL View Post
100% EtOH will help with HP but suck for fuel milage

well yeah! I run E85 on my stock car and MPG when down about 28% however, my 45whp gain thanks me every time I hit the throttle. I still get over 22+mpg on the highway. I didn't get my CORVETTE for gas mileage anyway

The only reason they put 15% gas in E85 so the red-necks wouldn't try to drink it (Moonshine anyone?)

The fastest race cars in the world use E85-100. Technology can handle a higher duty cycle in regards to injectors. It makes more power PERIOD.

Let me know if anyone wants to see my Dyno graph on a stock LS3 MN6
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Old 07-20-2011, 08:56 PM   #18
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Originally Posted by FNBADAZ06 View Post
Actually, it does matter. The factory 91 tune is using a stoic value for fuel that is based on 100 % gas, with no exception to the 10 % ethanol blend. This alters the "real" AFR slightly as well because of this stoic fuel difference. 100% pure gas has more power potential per volume than E10 so given the same injector flow you'll have more power and fuel economy with the 100 % gas product.

IMHO, a stock tuned car should make more power and get better fuel economy running straight gasoline as long as there's no KR
What he said ^
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Old 07-20-2011, 08:56 PM
 
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