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Old 09-30-2013, 12:54 PM   #1
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Ethanol ???

So I have been running 93 Octane with 10 ethanol but have found a place that sells ethanol free but at 91.5 octane. I have read artcles about the virtues of pure gas and wanted to know if anyone has experiance or information they would like to share.

I drive a 07 Boxster base.
Thanks.
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Old 09-30-2013, 01:14 PM   #2
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I would decide based on how quickly you go thru gas. If you turn it over frequently all year long, then it is not worth the extra cost. You won't feel the difference. If fuel sits in your car for months, then I would go with the non-ethanol. I run non-ethanol because i only drive this car 5,000 miles per year and it is stored for winter.
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Old 09-30-2013, 01:32 PM   #3
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Ethanol is baaad, mmmkay?

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Old 09-30-2013, 02:26 PM   #4
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In sweden we only have 95 and 98 octane and both have 5% ethanol, 10% is coming next year.
And 10% ethanol is Not Bad for 996/986.

But pure 91,5 octane sounds strange.
95 is the lowest a Boxster should be running on over here.

On the side note, it would be fun to see how much difference it would be with pure ethanol!!
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Old 09-30-2013, 03:06 PM   #5
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In sweden we only have 95 and 98 octane!
Octane is calculated differently in the U.S. Our 91 and 93 are the highest pump octanes available (racing fuel goes a lot higher), and are equivalent to European 95 and 98 octane.
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Old 09-30-2013, 03:09 PM   #6
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Ethanol is used as an oxygenate to promote lower emissions. It has a lower fuel value (BTU/lb mass) than gasoline. If I could get gasoline without ethanol I'd go that route and add a little octane booster.
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Old 09-30-2013, 03:10 PM   #7
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smy: the octane rating is different between the US and Europe. our 91 is your 95, our 93 is your 98...

personally, i'd rather the higher rating over pure gas.

the times i've been lucky to get a few tanks of "pure" gas have made a difference - slightly better MPG and better butt dyno result. but i've never tried the mid-grade pure. so you'll be trading one drawback for another. the engine will retard the timing and result in a loss of power, but most mid-grade is 89, not 91. technically i think 91+ is considered premium, though i've only seen it in high elevation locations.
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Old 09-30-2013, 03:52 PM   #8
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Aha, thanks for the info!
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Old 09-30-2013, 04:19 PM   #9
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I would decide based on how quickly you go thru gas. If you turn it over frequently all year long, then it is not worth the extra cost. You won't feel the difference. If fuel sits in your car for months, then I would go with the non-ethanol. I run non-ethanol because i only drive this car 5,000 miles per year and it is stored for winter.
I live where marine fuel is available and I can get 91.5 octane pure gas. Now besides water is it not also better for the seals?
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Old 09-30-2013, 04:21 PM   #10
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Ethanol is used as an oxygenate to promote lower emissions. It has a lower fuel value (BTU/lb mass) than gasoline. If I could get gasoline without ethanol I'd go that route and add a little octane booster.
Thanks for the info
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Old 09-30-2013, 04:38 PM   #11
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I've gone back and forth using both 100% 93 octane and 10% ethanol 93 octane, and I have monitored my mpg using an iPhone app (road trip). In two years, I have not seen a difference in mpg or power. Had I seen a difference, I would go out of my way to use the better fuel. I want to be an ethanol hater, but I have no empirical evidence .
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Old 09-30-2013, 04:49 PM   #12
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Ethanol is used as an oxygenate to promote lower emissions. It has a lower fuel value (BTU/lb mass) than gasoline. If I could get gasoline without ethanol I'd go that route and add a little octane booster.
So would it make sense that if you have pure gas it would equal better performance as even with 93 octane it has 10% ethanol that degrades performance?
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Old 10-01-2013, 05:10 AM   #13
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Pure gas has about 20-30% more "power" than ethanol, but we are only talking about up to 10% ethanol in your gas. Lets use 25% less power on that 10% of your fuel - that is a 2.5% difference. 93-91.5 octane is a difference of 1.6%. Either way, you can't feel or measure that in power or gas mileage.

Where I am willing to spend a little extra money is when my car is sitting and when I go to the track. And I would start filling with pure gas at least a fillup before my last fill so that when it goes in storage or to the track, the whole system is pure gas.

I would not add octane. The little tubes of it you get at gas stations and autoparts stores add like .1 octane. There are bigger cans of a worthwhile product called Race Gas that can actually bring fuel up to 100 octane, but that is not for the average situation.
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Old 10-01-2013, 06:39 AM   #14
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Octane rules. I'd rather use 93 octane with 10% enthanol than 91 octane pure gas.

To MonneyPit, until you've tested the fuel, you have no clue as to the alcohol level. I bought a test kit last year, and saw all kinds of crazy. I trust nobody as to "pure gas" claims. Testing octane, is much-much harder and very $$$$. So I just trust the retialer to be ethical, and only buy from major national chains (Mobil, BP and Shell).

As a side note, when I was testing my fuel for alcohol content, most was in the 5% range. All were below 10%. Very common to 8-9%. Which makes sense because of the cost of alcohol and they need to meet the claim at the pump for being "no more than 10%". So, I assume the shoot for 8-9% as not to exceed the 10%.
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Old 10-01-2013, 08:14 AM   #15
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Can you by ethanol at the gas station "over there"?

Over here its called E85 since its 85% ethanol and 75% in the the Winter.
Cars with turbo or Really High compression benefits from the 102 octane that E85 has.

Your miles to gallon is out the window, but the prize is lower so its nearly same same
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Old 10-01-2013, 07:26 PM   #16
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Pure gas has about 20-30% more "power" than ethanol, but we are only talking about up to 10% ethanol in your gas. Lets use 25% less power on that 10% of your fuel - that is a 2.5% difference. 93-91.5 octane is a difference of 1.6%. Either way, you can't feel or measure that in power or gas mileage.

Where I am willing to spend a little extra money is when my car is sitting and when I go to the track. And I would start filling with pure gas at least a fillup before my last fill so that when it goes in storage or to the track, the whole system is pure gas.

I would not add octane. The little tubes of it you get at gas stations and autoparts stores add like .1 octane. There are bigger cans of a worthwhile product called Race Gas that can actually bring fuel up to 100 octane, but that is not for the average situation.
Thanks for the math lesson as I forgot my HP:-)
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Old 10-01-2013, 08:05 PM   #17
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I don't think water is better for the seals.

Last edited by ganseg; 10-01-2013 at 08:26 PM.
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Old 10-01-2013, 11:24 PM   #18
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same question, which one is better.

91 gas with 0% ethanol

vs

94 gas 10% ethanol
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Old 10-02-2013, 07:55 AM   #19
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same question, which one is better.

91 gas with 0% ethanol

vs

94 gas 10% ethanol
the 94 with ethanol.

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