What’s better octane for an ecoboost?

[nastang87xx]

There's a lot of misguidance in here.

Ethanol != octane
Octane != ethanol

If a fuel is 91 it's 91 regardless of the ethanol content. 100% gasoline 91 octane rated fuel is still 91 as is 90% gasoline + 10% ethanol 91 rated fuel is still 91. YOU DO NOT GET ANY ADDITIONAL KNOCK RESISTANCE FROM ADDITIONAL ETHANOL IF YOU FUEL IS RATED FOR A FIXED OCTANE RATING.

Go look at an E85 pump. Notice anything? No sign of an octane rating anywhere. E85 is actually a mystery when it comes to what Octane rating you're really at. And in some areas E85 isn't always 85% ethanol either. It will depend on your local/state laws on what E85 is. Example, some laws will say all they owe you in the fuel is 75% ethanol. GENERALLY though most E85 is above 100 octane equivalent.

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[Deleted member]

There's a lot of misguidance in here.

Ethanol != octane
Octane != ethanol

If a fuel is 91 it's 91 regardless of the ethanol content. 100% gasoline 91 octane rated fuel is still 91 as is 90% gasoline + 10% ethanol 91 rated fuel is still 91. YOU DO NOT GET ANY ADDITIONAL KNOCK RESISTANCE FROM ADDITIONAL ETHANOL IF YOU FUEL IS RATED FOR A FIXED OCTANE RATING.

Go look at an E85 pump. Notice anything? No sign of an octane rating anywhere. E85 is actually a mystery when it comes to what Octane rating you're really at. And in some areas E85 isn't always 85% ethanol either. It will depend on your local/state laws on what E85 is. Example, some laws will say all they owe you in the fuel is 75% ethanol. GENERALLY though most E85 is above 100 octane equivalent.

When the gas companies are using ethanol to increase the octane level in gas to get it to whatever it is rated at, then yes its adding knock protection. E85 being a true 85% or not has nothing to do with it, Ethanol no matter what the mix ratio is, is 100 octane or higher as you stated, ive yet to see a test with ethanol showing the octane rating under 100. Therefore the higher the percentage of ethanol mixed in with the gas then the higher the octane rating of that mixed fuel will be.

I've experimented with this by adding about 1-1.5 gallons of E85 to 91, this is not enough to be a true E30 mix which of course my E30 tune requires. I run my 91 octane tune when i do this, and my knock count is drastically reduced. So im sorry but you can't sit here and tell me that mixing a higher octane fuel with a lower octane fuel won't somewhat raise the octane.

If that were the case than what the hell would be the point of running E30/E50/E85????

 

[shogun32]

Go look at an E85 pump. Notice anything? No sign of an octane rating anywhere...And in some areas E85 isn't always 85% ethanol either.

Here in northern virginia the signs at Sheetz stations says '94' but there is also legible type that says the Ethanol content may vary between 50 and 85 depending on season and refinery pique.

GENERALLY though most E85 is above 100 octane equivalent.

I think that's a dangerous assumption. If you buy a barrel of E85 straight from a fuel distributor it will be certified to some number, roughly around 98. If you go for 'race fuel' grade that can go around 103. If you want true high-test you'll want to get unleaded general aviation fuel in the vicinity of 110. But what that'll do to your emissions I have no idea.

If you want to run some kind of Ethanol fuel, you really have to test each dispenser and make choices appropriately. There is nothing 'magical' about Ethanol and knock resistance vis a vis whatever else is in your tank. If the mixture is rated at 93 it behaves the same WRT knock whether it's 100% "pure" gasoline or 5%.

 

[MikeHTally]

Here, 93 is $2.83 at Costco. 87 is $2.35. Actual fuel cost/mile is $0.1275 vs. $0.1120 (guessing the mileage will drop slightly with 87). So, 93 costs $0.015 more per mile. I'll keep the 93. For the minuscule extra cost, I'll take the performance gain.

It is good to know I can use 87 if I have no alternative, though. My Mazda's book said ONLY enough 87 to get to some 91+.

 

[nastang87xx]

I think that's a dangerous assumption. If you buy a barrel of E85 straight from a fuel distributor it will be certified to some number, roughly around 98. If you go for 'race fuel' grade that can go around 103. If you want true high-test you'll want to get unleaded general aviation fuel in the vicinity of 110. But what that'll do to your emissions I have no idea.

If you want to run some kind of Ethanol fuel, you really have to test each dispenser and make choices appropriately. There is nothing 'magical' about Ethanol and knock resistance vis a vis whatever else is in your tank. If the mixture is rated at 93 it behaves the same WRT knock whether it's 100% "pure" gasoline or 5%.

I wholeheartedly agree.

 

[nastang87xx]

When the gas companies are using ethanol to increase the octane level in gas to get it to whatever it is rated at, then yes its adding knock protection.

91 is 91 regardless of the ethanol blend. Ask any tuner if they would recommend a 93 tune using 91 just because it has E15 or E20 blend.

I'll take the liberty of getting their contact info

VMP: 321-206-9369
Lund: [email protected]
AED: 916-715-7569

 

[Deleted member]

91 is 91 regardless of the ethanol blend. Ask any tuner if they would recommend a 93 tune using 91 just because it has E15 or E20 blend.

I'll take the liberty of getting their contact info

VMP: 321-206-9369
Lund: [email protected]
AED: 916-715-7569

Again you are completely missing my point.
Not all 91 is created equal(different stations,different additives,ethanol blend ratios,tanks that the fuel sits in) are all gonna change the quality of your gas. Especially here in California, i doubt most places are selling a true 91 octane our fuel quality is complete sh**.

I've never said that ethanol is magical knock protection(octane is the knock protection), but it DOES raise the overall octane rating of the gas it is mixed with. This is proven, period, end of story.

The car can't tell what the F88k is in the tank! Whatever fuel your car is tuned for, there are set parameters for timing fuel etc as im sure you know. If a car tuned to run on 91 has higher octane fuel in the tank its going to be able to max out the timing parameters set for that tune, but still not maximizing the fuels full potential. If the same car on a 91 tune has 87 put in the tank, you're going to have pre-det causing knock therefore reducing timing and power...

I'm not saying running a blend is going to magically make your car more powerful, but it will add knock protection period. An engine does not need to be tuned for the higher octane fuel for it to help prevent pre-det....

I also never recommended running a higher octane tune on a lower octane fuel mixed with E85. I said in my personal experience when i add a small amount of e85 on my 91 tune while also filling the car with 91, that i see added knock protection in daily driving low load situations that is all.

Stock fuel system on a eco can handle a mix of ethanol up e30 just fine.

Yes you need to test your local stations e85 to see its true content to get a truly accurate mix, which i do while running a true e30 tune. My local stations varies month to month but is usually 75%+ ethanol when tested.

 

[Stealthfall]

Here in northern virginia the signs at Sheetz stations says '94' but there is also legible type that says the Ethanol content may vary between 50 and 85 depending on season and refinery pique.

I think that's a dangerous assumption. If you buy a barrel of E85 straight from a fuel distributor it will be certified to some number, roughly around 98. If you go for 'race fuel' grade that can go around 103. If you want true high-test you'll want to get unleaded general aviation fuel in the vicinity of 110. But what that'll do to your emissions I have no idea.

If you want to run some kind of Ethanol fuel, you really have to test each dispenser and make choices appropriately. There is nothing 'magical' about Ethanol and knock resistance vis a vis whatever else is in your tank. If the mixture is rated at 93 it behaves the same WRT knock whether it's 100% "pure" gasoline or 5%.

Be careful with aviation fuels. As of right now majority of Aviation Gasoline is still leaded 100 Green dyed and 100LL blue "Low lead" is still a fairly high lead content .56 grams/Litre. Unleaded is "still in testing" (debatable as i think it stalled) with the FAA so availability will be questionable at best.

 

[WildHorse]

Is 90 without ethanol better than 91 or 93 with ethanol for performance?

No, 93 would be the best.

 

[w3rkn]

Again you are completely missing my point.
Not all 91 is created equal(different stations,different additives,ethanol blend ratios,tanks that the fuel sits in) are all gonna change the quality of your gas. Especially here in California, i doubt most places are selling a true 91 octane our fuel quality is complete sh**.

I've never said that ethanol is magical knock protection(octane is the knock protection), but it DOES raise the overall octane rating of the gas it is mixed with. This is proven, period, end of story.

The car can't tell what the F88k is in the tank! Whatever fuel your car is tuned for, there are set parameters for timing fuel etc as im sure you know. If a car tuned to run on 91 has higher octane fuel in the tank its going to be able to max out the timing parameters set for that tune, but still not maximizing the fuels full potential. If the same car on a 91 tune has 87 put in the tank, you're going to have pre-det causing knock therefore reducing timing and power...

I'm not saying running a blend is going to magically make your car more powerful, but it will add knock protection period. An engine does not need to be tuned for the higher octane fuel for it to help prevent pre-det....

I also never recommended running a higher octane tune on a lower octane fuel mixed with E85. I said in my personal experience when i add a small amount of e85 on my 91 tune while also filling the car with 91, that i see added knock protection in daily driving low load situations that is all.

Stock fuel system on a eco can handle a mix of ethanol up e30 just fine.

Yes you need to test your local stations e85 to see its true content to get a truly accurate mix, which i do while running a true e30 tune. My local stations varies month to month but is usually 75%+ ethanol when tested.

I think what he is saying is that you would get the same thing if you just went with 93 octane instead. It not like pure eth that is preventing knock, it is the higher octane.

 

[Bluemustang]

There's a lot of misguidance in here.

Ethanol != octane
Octane != ethanol

If a fuel is 91 it's 91 regardless of the ethanol content. 100% gasoline 91 octane rated fuel is still 91 as is 90% gasoline + 10% ethanol 91 rated fuel is still 91. YOU DO NOT GET ANY ADDITIONAL KNOCK RESISTANCE FROM ADDITIONAL ETHANOL IF YOU FUEL IS RATED FOR A FIXED OCTANE RATING.

Go look at an E85 pump. Notice anything? No sign of an octane rating anywhere. E85 is actually a mystery when it comes to what Octane rating you're really at. And in some areas E85 isn't always 85% ethanol either. It will depend on your local/state laws on what E85 is. Example, some laws will say all they owe you in the fuel is 75% ethanol. GENERALLY though most E85 is above 100 octane equivalent.

Correct. Octane = knock resistance level. Ethanol does not = that.

 

[TicTocTach]

May have been stated a dozen times in different ways, but a condensed version is probably useful:

In terms of its octane rating, ethanol has a rating of 113. As mentioned above, fuels with a higher octane rating reduce engine knocking and perform better. Also, almost all gasoline in the US contains 10 percent ethanol. When you mix 10 percent 113 octane ethanol with 85 octane gasoline it increases the octane two points to the normal 87 octane most consumers use. So the higher the ethanol content, the higher the octane. The octane rating for E15 (15% ethanol) is 88 octane and E85 (85% ethanol) is 108 octane.

Copy/paste from here: https://mnbiofuels.org/media-mba/blog/item/1511-octane-and-ethanol-for-beginners

It's really just a ratio or weighted average kind of thing, and a comparison to the original gasoline formulations.
https://en.wikipedia.org/wiki/Octane

 

[shogun32]

per http://www.wallaceracing.com/ethanol-mix-calc.php
The octane of E85 can be from 100 to 105 or so.
It is not a straight change with the addition of gasoline.
(100% ethanol around 115/120 octane, E85 is around 100/105 octane and it drops quickly after that)
It is suggested that 100 octane be used for E85 in this calculator to give a more accurate octane rating when mixed (diluted) with gasoline

I had a spec sheet from a Wisconsin(?) fuel distributor that claimed their E85 you could buy in 55 gallon drums at a time was certified to 98oct. Clearly there is quite a range on the so-called octane rating of the various mixes.

This is a pretty cool one. Even has an EB setup defined.
https://adamtuned.myshopify.com/pages/tuning-tools

 

[RedEcoJet]

FWIW, l have 131k miles on my EB and have always run 93. The exception being a couple of times in New Mexico where 86 was the best they had. I drove very conservatively until I could get 93.

JerryA

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