question about 93 E10

[dailydriver]

Ethanol can be an octane booster, despite the abject hatred for the stuff (mostly) on here, as some performance aftermarket tuners actually suggest up to an E40 blend of E85 fuel with PREMIUM 91/93, on specifically tuned for it, high boost/output (and compression) scenarios.

That being said, I was curious as to HOW the 93 octane, E10 content premium fuels are blended, even though yes, 10% ethanol will barely raise the actual octane of the fuel a small/minuscule fraction of a point.

Is 10% ethanol added to pure/'neat' fuel which is already at 93 octane additive levels, or are those additive levels adjusted downwards to compensate for the added octane of the added ethanol (no matter how little octane is added for a 10% ethanol level), to yield the 93 octane rating?

 

[MNgopher]

Typically any E10 fuel is created by blending 10% ethanol with a lower octane base fuel to reach the desired octane rating. Thus 93 Octane is typically 91 octane gasoline blended with 10% ethanol.

(Most 87 octane E10 fuels are created by blending a sub-octane fuel, roughly 85 octane with 10% ethanol).

In other words, the 10% ethanol blend is roughly a 2+ octane rise in octane rating. You are getting what the pump advertises, not some octane 2 points higher...

 

[jhellwig]

10% ethanol raises octane 2 to 3 points. E10 93 is made with ethanol and 91 octane. E10 87 is made with ethanol and 85 octane. If you see an octane between 87 and 91 without ethanol it is made by blending 91 octane with 85 octane. E10 89 octane is made with ethanol, 91 and 85.

I have noticed some stations have something called super 88 or something that is 88 octane. I believe this is what is also referred to as e15. 15% ethanol and 85 octane.

 

[KeithS_NW_Ohio]

E10 87 starts as 84 octane.

 

[Revving2Redline]

93 E10 at Murphys in Leavenworth,KS by Eisenhower Street. I use it during summer sparingly to top off 87 Pure but I am careful to keep my ethanol content below 5% running Redline oil.

https://itstillruns.com/effects-ethanol-catalytic-converter-12172217.html

High zinc and phosphorus not good with alcohol.

 

[y_p_w]

It's roughly about 2 or more AKI points. These days they won't take 93 AKI ((R+M)/2) fuel and blend it with 10% ethanol to get something higher. However, it's really a math exercise. 10% ethanol will result in a slightly higher point boost when blended with a lower octane rated base fuel. Obviously if you could manage to make a non-ethanol fuel that has exactly the same octane rating as ethanol, blending it will result in the same octane rating for the blend. I've heard different numbers for the blending octane rating of ethanol - anywhere from 98 to 104 AKI.

I believe they may actually try to ensure that it's a little bit higher than exactly 87/89/91/93/94/etc, but not excessively so. The pump sticker always says "MINIMUM OCTANE RATIING".

These days pretty much all base fuels that are blended with ethanol are designed with it in mind to achieve the target octane rating. The most common commodity fuel today in the US is "Reformulated Blendstock for Oxygenate Blending" or RBOB. It's around 84 octane but achieves at least 87 octane when blended with 10% ethanol.

There is an industry term for the way it used to work when they'd make (for example) 92 octane fuel before blending with an oxygenate, and afterwards the octane rating would be boosted. It was called "octane giveaway". These days there are smaller amounts of this, and even then apparently it's considered a cost savings to try to make sure it's not excessively higher than the rated octane. Here's a paper that refers to that from 1999. This calls fuel meeting the pump octane rating before ethanol blending "specification-grade".

Quote
https://www.nap.edu/read/9714/chapter/12
Thus, when ethanol is blended at a terminal, the blend stock is specification-grade gasoline. The addition of 10 percent ethanol to regular gasoline produces a blend with an octane number about two units above the number required for regular gasoline. This causes an octane giveaway when the ethanol blend is sold as regular gasoline.

 

[dailydriver]

THANKS everyone!

This is what I've suspected, but given the economics of corn production, I was not sure.

 

[y_p_w]

I know there's a lot of distaste for fuel ethanol, but it certainly has its place as an oxygenate. MTBE is increasingly difficult to use for any number of reasons, including that half of all states have banned it. I don't know of any manufacturer that currently approves of the use of methanol, although I remember reading through a model year 1989 owner's manual that said up to 5% was OK as long as it included corrosion inhibitors.

But there are certainly incentives to use some sort of oxygenate. For one, ethanol is cheaper (without subsidies) than gasoline blendstock. Granted it's got about 2/3 the energy content, but that's a given. These days there are so many vehicles that recommend/require 91 or 93 AKI octane that it's hard to make enough of it relative to other crude oil products that it needs some sort of octane booster. Ethanol is simply the cheapest and most acceptable at this point. Refiners are apparently doing what they can to make higher octane products out of crude oil (using chemical processes), but I hear that has its limits.

I heard that it used to be possible to take unsold parts of the refining process and pump them back into the ground, but I believe that's not allowed any more. So these days they're doing everything they can to sell everything. And ethanol helps a lot.

 

[dailydriver]

Yes, IF I had an E85 dispensing station within 50 miles of me, I would get a tune, and blend it with the 93 E10 sold here to give an E30 yield, and a nice jump in power on the factory turbo, yup, even despite the MPG 'hit' everyone on here would cry about.