Dumb Question which is Better - 93 Octane or Ethanol Free? - Porsche Macan Forum
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Old 06-13-2019, 09:01 PM Thread Starter
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Question Dumb Question which is Better - 93 Octane or Ethanol Free?

So one of my favorite Convenient Stores for Gas...

Has always had 93 Octane which I have used in my Macan.
But now they have Ethanol Free which is a few cents more.

Which is better? 93 Octane or Ehtanol Free?
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Old 06-13-2019, 10:46 PM
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So one of my favorite Convenient Stores for Gas...

Has always had 93 Octane which I have used in my Macan.
But now they have Ethanol Free which is a few cents more.

Which is better? 93 Octane or Ehtanol Free?
I HATE ethanol, so the choice is easy.
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Old 06-13-2019, 11:28 PM
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No question is a dumb question.

Gasoline has 114,000 BTU per gallon and ethanol has 76,100. So gasoline has about 1.5 times the fuel density. This means that, in theory, a car that gets 20 mpg on pure ethanol will get 30 mpg on pure gasoline.

Standard E10 is gasoline with 10% ethanol so it has 110.2 BTU per gallon, or 97% the fuel density of gasoline. So if your car gets 20 mpg on E10 it will get 20.7 mpg with gasoline.

Based on fuel millage alone if you can get pure gasoline for 3% more than E10 it's a good deal.

I don't think you would see any other performance difference.

I prefer to use pure gasoline in my outdoor power equipment where I may not use a tankful quickly. The reason is that the ethanol absorbs water from the atmosphere, and the water can cause rust in internal parts. Left long enough, the alcohol turns into a shellac type substance that can cause valves to stick and ruin the engine.
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Old 06-13-2019, 11:28 PM
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Not a stupid question. Another (important) question would be: What is the octane rating of the ethanol free?

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Old 06-13-2019, 11:51 PM
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Ethanol free is great for lawn mowers, chain saws all yard tools due to the rubber parts in the carburetor that dissolve when exposed to ethanol. You go thru fuel so quickly in your Macan it has no chance to work against rubber parts and your not looking a carburetors to rebuild.

The plus for your car is ethanol free gas improves mileage by about 10% versus gas with ethanol. If the price you state is within pennies I’d run ethanol free. When I had it available the cost differential was close to $.85 cents a gallon for ethanol free so the mileage improvement did not offset the cost difference.

The car requires a minimum 91 octane so if your paying extra for 93 octane your wasting money. If your running a Cobb tune they as well will tell you to run the 91 octane tune even if 93 is available. All in all it depends what you have in you local market when I lived inPNW we did not have 93 octane and have over 40000 trouble fee miles running 91 octane with ethanol.

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Old 06-26-2019, 05:51 PM
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your correct Yadkin about the BTU
But you must also add in the following (much quicker burn rates, higher temp, moisture n evaporation issues) Loss of power and byproducts from the GMO Corn alcohol..... YUCK!
Yes, Real 100% Pure Gas is the Best/Only way to Go!
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Old 06-27-2019, 11:53 AM
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+1 for ethanol free. Wish we even had that in my neck of the woods. 93 has been good thus far.

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Old 06-27-2019, 06:51 PM
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Not a stupid question. Another (important) question would be: What is the octane rating of the ethanol free?
This is the most important question
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Old 06-28-2019, 01:05 AM
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I hate ethanol but unless I am near a boat yard it is difficult to find.

Some years ago I had a Ducati Paul Smart. As soon as the state added ethanol to our fuel the Paul Smart's plastic tank began to warp. I went through three tanks before I sold the bike.

Fortunately our cars are designed to work with ethanol.

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Old 06-28-2019, 08:35 AM
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I don't want to get into an R vs. D issue here, but I think the ethanol in gas policy in the US is a good one. Before that the government used to pay farmers to grow nothing; the theory being that farmland had to be preserved. Now we pay them to grow corn to burn in our cars. If WW3 happen and all of a sudden we have to produce a ton more food, we can feed a lot of people with corn in the short term and that land is available for other crops.

For the vast majority of drivers who drive Toyotas and Hyundais it's not an issue. It's not an issue for me in my daily driver Macan because I go through it so fast. I manage it easily in my two classic cars (although I learned how the hard way). And for those who insist on E-free, for most anyway, there are options.

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