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Discussion Starter · #1 ·
Just got our Cayman. Search shows this was asked a few years ago but I thought I'd ask again. I can get 91 octane ethanol free locally. Would it be better to use it or the 10% ethanol 93 octane at other stations? Damned ethanol eats small engines if you don't treat it with Sta-bil or similar so I wonder what it does to the 2.7.
 

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Just got our Cayman. Search shows this was asked a few years ago but I thought I'd ask again. I can get 91 octane ethanol free locally. Would it be better to use it or the 10% ethanol 93 octane at other stations? Damned ethanol eats small engines if you don't treat it with Sta-bil or similar so I wonder what it does to the 2.7.
You have it from an authoritative source that using gasoline with ethanol has damage any Porsche engine? Source?
 

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Discussion Starter · #3 ·
No, I don't have a source for automotive engines, but my guy at the outdoor power equipment shop (chain saws, blowers, etc.) says the stuff is lethal for small 2 stroke and 4 stroke engines. Just wondering what effect it has on bigger engines, if any. Enquiring minds need to know.:)
 

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No, I don't have a source for automotive engines, but my guy at the outdoor power equipment shop (chain saws, blowers, etc.) says the stuff is lethal for small 2 stroke and 4 stroke engines.
I would not disagree with his assessment but I don't think he mentioned the entire reason. See this Gasoline Expiration - Ethanol Blend Fuels Have a Short Shelf Life. The problem is people store gasoline year round and then put it in their lawn mower or generator but due to the short shelf life it gums up the carburetor. I have seen this happen and had to rebuild carburetors. Stabil solves that problem.

If the gas is sitting in your car for three months unused, then I might start to worry about it. And many p-car owners do have their cars sit all winter so it might not be bad idea to add stabil. But cars sitting a couple of months - its not an issue.

Bottom line, I wouldn't worry about it for normal driving or cars sitting around for a couple of months. For cars sitting for 6 months, I might.

Good luck.
 

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Discussion Starter · #5 ·
Thanks. So it would be OK to add Stabil to the tank for storage next winter? Say December through February? Just to be safe?
 

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This article thinks so, #8 Storing your vehicle

That said, there are several posters here who put their cars up for many months during the winter and I will defer to their experience. I do not. If the temperature is above 40 degrees and no salt on the road, I drive it.

I am sure others will jump in here.
 

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I've left a non-P car (MR2 Turbo) for 9 months several times, added the can of Stabil that everyone tells you to use, hooked up a battery tender, and all was fine--not even flat spots on the tires!
 

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I've used only 92 octane non-ethanol, which I believe contributes to the great gas mileage I'm getting. On my last two trips of about 50 miles each, I got 37 & 38 mpg on I-5, going with the flow of the traffic. Also use it in my chain saw & lawn tractor, as the ethanol screwed them up.
 

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I believe these engines are fine on the current 10% blends (although I would definitely add Stabil or Star Tron if the gas was going to be in the tank for a few months for all the reasons mentioned above). I am very concerned however about the push to 15% ethanol! I really think the "jury is still out" on that. I realize it is not widespread yet but the government does seem to pushing that way and I just don't see a station trying to carry both the 10% and 15% versions.

That said, back to your original question -- I would definitely try the the 91 octane and see if I noticed any performance issues (I'm guess the computer will make the necessary adjustment and you won't notice anything). And, if it seemed fine I would much prefer the non=ethanol option.
 

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My 2 cents ...

Having owned an Audi RS4 that was infamous for having issues with carbon deposits (after a proper carbon cleaning the performance was substantially improved), I did a fair amount of reading about the likely causes ... It is believed that ethanol contributes to this. I stopped using gas with ethanol (93 OCT) and started using Shell 91 which is the only non ethanol gas available near me. I didn't own the RS4 long enough to scope the engine after prolonged use with the Shell 91 but did scope the TTS that replaced it after a couple years of daily driving and it was not gummed up like the RS4. The other benefit to using non ethanol gasoline is that most recognize improved gas mileage which i understand is due to ethanol requiring more energy to burn. A down side to reduced octane gas is the potential of pinging or knocking; however, my TTS was modified with a tune and full exhaust and I never had any issue with regular spirited driving in hot humid weather ...
 

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My base Boxster normally gets 93 E-10 as there is no non-ethanol gas available within about 100 miles. However on a trip to eastern Canada in 2013, I used only ethanol free 91 octane and there was no discernible performance difference, but gas mileage improved by about 3 or 4% as expected.

I also add Stabil if the 981 is not run for more than 2 months.
 

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It will require about 20 bottles of the typical octane booster to raise a tank of gas from 91 to 93.
That is correct. The bottle says it will raise a tank of gas by "up to three points." What they don't tell you is that three "points" is only .3 octane.

- Patrick
 

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That is correct. The bottle says it will raise a tank of gas by "up to three points." What they don't tell you is that three "points" is only .3 octane.

- Patrick

Shows you what I know. I just contribute to brainstormimg activity as an idea guy lol. A.k.a. Not the expert
 

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Here's you need to think about. Ethanol is much more perishable than 100% gasoline. It does not store well or for very long, compared to straight gasoline, which is one reason oil companies don't like it. Think of ethanol blend like fresh milk. It might be a week or maybe as long as two weeks from refinery to your tank, and then if it is in your tank for long, it can go bad, causing increased corrosion and deposits. Ethanol raises octane rating when added to gasoline, but mpg and possibly power will drop because it produces less energy per gal than 100% gasoline. Because ethanol is perishable, you won't want to store your car with it, Stabil or not. You can use either when it's your daily driver, but when you want to store your car with fuel left in the tank more than 10-14 days, you need to have already switched to straight gasoline. One or two winters storage with it probably won't do great damage but whatever effects it has will accumulate over time. Ethanol blend might result in lower hp in a race car, especially at higher air densities, but probably not in these production cars designed to use ethanol blends. You will certainly get better mpg with straight gasoline, but not all ethanol blends are 10% ethanol. As the signs on the pumps say, this fuel may contain up to 10% ethanol. Not every station's tanks have the full 10%. The suppliers just have to use certain overall amounts of ethanol, and this may vary by region and season, and certainly varies by truckload and perhaps locally by octane rating, at the convenience of the supplier. The other question is, is the straight gasoline worth the extra cost for a daily driver? What is the price differential? There are tradeoffs.

Ethanol was mandated for use in US motor fuels for political reasons. They claimed it was for cleaner air and the planet. It had done some good things here, but some unintended effects have not been good elsewhere That's all I should say here.
 

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93 Octane w/ ethanol is perfectly fine for modern Porsches. They are designed to run well on 10% ethanol. The 91 octane 100% gasoline may give you better mileage (because ethanol contains less BTU's, not that it requires more energy to burn), but it will also give you less power as the ECU will adjust your timing and spark to run on the lower octane without knocking.
If the car is stored for several weeks/months, Stabil is a definite aid you should consider, but for regular use, just drive it. Ethanol is very hygroscopic, meaning it absorbs water. This causes problems the longer it sits as it has more opportunity to absorb moisture.

Small 2 cycle engines definitely don't like ethanol, and you will see most landscape companies filling up their equipment and portable gas tanks at stations that sell 100% gas. This is not an issue with newer cars, but with weed eaters, snow blowers, leaf blowers, etc. I've never put a drop of ethanol in my 2 cycle equipment and I have a 18 yr. old string trimmer that still runs fine and has never had any problems. I used to obsess over ethanol, and drove miles to find gas without it, but after discussing this with several oil company people and car mfg. types I've come to the conclusion that it is unwarranted. So now I just fill up at the local Citgo that carries 93 octane 10% ethanol. If I happen to find 92 or 93 octane 100% gas I'll use it and get a little better mileage, but otherwise I just DRIVE.

I used to be in the gasoline business, an Exxon/Unocal/Citgo/Conoco branded distributor and had access to lots of information regarding ethanol. I got out in 2006 and never sold ethanol due to my aversion to it and my objection the the political reasons for its use in the first place. It still makes no sense, but fighting it right now is useless.
 

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Had a problem once with rubber fuel lines deteriorating that might have been due to ethanol. "Ethanol has been known to wreak havoc on fuel systems, deteriorating plastic and silicone components such as hoses, fuel pumps and filters, gas tanks, and fuel injectors." link
 

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Had a problem once with rubber fuel lines deteriorating that might have been due to ethanol. "Ethanol has been known to wreak havoc on fuel systems, deteriorating plastic and silicone components such as hoses, fuel pumps and filters, gas tanks, and fuel injectors." link
That was also on cars built not in the ethanol days. My 1964 ford also had problems eating valves after lead was removed until I rebuilt the heads with hardened valve seats. Modern cars of today are designed to run with some or a lot of ethanol and as always read your manuals. They provide the limitations of fuel grades and compositions along with other useful information.


Sent from my iPhone using Tapatalk
 

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Before ethanol became common lots of cars had problems with it, the gas pumps at stations did also. Even some of the fiberglass underground tanks essentially dissolved because of the solvent qualities of ethanol. All that has changed now, cars are designed with hoses and seals that are compatible with ethanol, and this has been the case for over 10 years. Older cars, yes they have problems, and if I had say, a 70's muscle car I'd find a good source for high octane 100% gas. Many cars now have plastic gas tanks instead of steel, and they too are designed to work with ethanol. My earlier comments are still valid.
 
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