no ethanol 93 octane - Subaru WRX Forum
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#1 Old 06-05-2014, 10:37 AM
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no ethanol 93 octane

Just noticed yesterday that a gas station where i live offeres a no-ethanol 93 octane fuel. My question would I want to avoid this or run it in my car?

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#2 Old 06-05-2014, 12:40 PM
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Quick answer -- if it costs more skip it, if the price is the same choose it and if its cheaper buy it by the barrel.

Long answer -- Lots of fuel contains ethanol for a handful for reasons. thanks to agricultural subsidies and monsanto GMO corn in the united states there often goes to waste a tremendous amount of corn product, In alot of cases it is more cost effective for farmers to grow the corn and let it rot rather than sell it at a loss (if they can even sell it, lots of folks afraid of GMO corn) What they figured out is that you could process (read: ferment and distill) the excess corn product into a "viable" fuel. That means that farmers don't have to let their crops rot in the fields because they cant sell them above their subsidies cost to fuel manufacturers.

Viable is in the eye of the beholder, I burns great but its also pretty nasty stuff around plastics and rubbers, Ethanol is less stable than gasoline and cause some metals to corrode. Ethanol is also hydroscopic meaning it likes water and will grab moisture from the surrounding air, the greater the water content in your fuel the less power it can produce. on average a gallon of 100% ethanol contains 30% less energy than a gallon of gasoline but it has a MUCH HIGHER OCTANE RATING. That means that you can use forced induction to a greater degree with ethanol than you can with standard gasoline.

Enter E85, Many drivers of forced induction performance cars enjoy E85 for its high octane rating ( between 100-105 ) They also sugest that because of its higher octane levels it can be safely run under greater pressure and heat with a leaner mixture to produce more power.

The balance in many fuel stations in america is up to 15% ethanol. That means that up to 15% of your "gasoline" can come from ethanol. That means they could be using the ethanol in the mixture to raise the octane rating of lower quality fuels or they could be addidng it to help them stay price competitive because it is cheaper to produce ethanol than gasoline. Either way most modern engines can handle a bit of ethanol without tremendous side effects. Sure its bad for rubber hozes and slowly corrodes most metals but its not going to make your engine blow up running with some ethanol.

If I have a choice I will choose top teir 91 octane Non-ethanol for my stage 1 WRX but i wont pay extra for it because there is no meeasurable performance gain. I run Shell 91 Octane (May contain up to 10% Ethanol) religiously so take everything with a grain of salt.
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#3 Old 06-06-2014, 01:19 PM
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So then could you use e85 on a stock WRX without any special tuning? And how would that effect the engine long term, based on its deteriorating tendencies. Also, how does 91 differ from 93, in terms of octane? I also use shell v power religiously (FRN card, baby) so I'm curious to see whats up.
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#4 Old 06-06-2014, 03:56 PM
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Originally Posted by Nekronaut View Post
So then could you use e85 on a stock WRX without any special tuning? And how would that effect the engine long term, based on its deteriorating tendencies. Also, how does 91 differ from 93, in terms of octane? I also use shell v power religiously (FRN card, baby) so I'm curious to see whats up.
You would NOT run E85 on a stock WRX beacuse the ECU is not tuned for the power and octane difference. to over simplify it would use too little E85 and could cause knock or other issues. It would also be very slow because the optimum ratio for burning gasoline in air is different than E85. the tendency for E85 to deteriorate vehicles is really a matter of preperation. Replacing butyl rubber hoses with SS lines would go a long way to preventing issues but it does eat through alot of fuel handling parts. If you are planning on going the E85 route get fuel lines, sending unit, injectors and fuel rails that support E85, they are typically made of non-reactive materials and can handle the added volitility.

When we talk about E15 91 octane we mean fuel with a mixture of gasoline and "up to 15% Ethanol" that means that the e15 fuel should burn very similar to 91 octane gasoline albeit cleaner and less powerful.

The octane level of fuel determines the fuels ability to handle heat and pressure without flashing. a higher octane rating means that a fuel can be compressed (forced induction by means of turbo) and heated ( additional heat generated through compression) without pre-igniting. To put it simply a gallon of 93 octane fuel at a 1:13 air fuel ratio will self ignite at a higher pressure than a gallon of 89 octane in the same conditions.

**With proper tuneing** you can run more boost with higher octane fuels. E85 is often rated near 100 octane and because it can handle much greater pressures than normal pump 93 racers prefer it for their very high boost vehicles.

TLDR--DO NOT USE E85 ON A STOCK WRX
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#5 Old 06-06-2014, 05:10 PM
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The only thing you need for E85 is a pump and injectors, with a tune of course. The 15% is enough to keep everything lubed up properly. There are cars with stock lines and e85 with no issues that have had that set up for years.

Ethanol is used in modern fuels in the US because the clean air act required fuels to be oxygenated, they were using MTBE at first, but it started showing up in our drinking water. So they switched over to ethanol as it was a safer replacement.
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#6 Old 06-09-2014, 01:48 PM
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E85 can be a performance boost. Higher octane, you can turn up the boost. That said, you need more VOLUME of E85 than you do dyno oil. Your fuel consumption will increase. E85 should be (isn't always) considerably cheaper than dyno oil so this should balance out the added consumption.

E85 means you have to retune, limit your refueling options (tune for one or the other, not both), suffer lower gas mileage, and change some relatively minor fuel related parts. In return, you get the benefits of higher octane gas (more air, more power).

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#7 Old 06-09-2014, 03:54 PM
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E85 means you have to retune, limit your refueling options (tune for one or the other, not both), suffer lower gas mileage, and change some relatively minor fuel related parts. In return, you get the benefits of higher octane gas (more air, more power).
This is true. It is not cheap though. I spent at least 2000 in order to add a fuel system capable of running E85 as well as the E85 tune. At least that is what I remember it being though....
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#8 Old 06-09-2014, 04:24 PM
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You can get a dual map tune though, so even with your bigger injectors you can still switch back and forth between fuels. Most tuners will do it at a discounted price for the extra map.
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#9 Old 06-10-2014, 10:24 PM
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Thanks for the info guys! I'm learning a lot here. Never too much of that.
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#10 Old 06-16-2014, 06:33 AM
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You can always use E85 to rule out bad fuel as well.

ie... adding a gallon to a full tank (almost full) and see if knock subsides. I do this often in the FXT with no known issues to report in 2+ years.

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