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Discussion Starter · #1 ·
I have a very stock 2007 GT with CAI and SCT/Bama tune.

Recently a local gas station put in a blending pump. For those of you not familiar, this is becoming more popular where E85 is offered, you can select E10 (which is 89 octane), E20, E30, E50 and E85. Functionally what happens is, E10 is blended with E85 in the appropriate proportion. The 20 and 30 aren't labeled for octane but from what I gather the 20 is in the low to mid 90s octane and naturally the 30 is a bit higher than that.

I'm happy to see these offerings because 93 is hard to find here and 91 is expensive and already has 10% ethanol. Prices for 20 and 30 are lower than 89 octane (E10).

I currently have a "race" tune which is set up for 93 octane.
Are the 20 and 30% blends enough different to require a new SCT tune or will the oxygen sensor have enough range to adjust?

One of my concerns is the cats (which are stock) running too hot and being damaged.
 

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Ethanol will run cooler. Yes, you do need a tune. It has nothing to do with the 02 sensors adjusting. The stoich level of gas is much higher than ethanol.

Gas doesn't have 10% ethanol in it, it CAN have up to that amount but it doesn't mean you're getting that. Same with E-fuels. You will notice how you run lean if you don't get a tune, dangerously lean if you try the E-blend without a tune.
 

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Discussion Starter · #3 · (Edited)
I see what you are saying about the O2 sensors. Whatever the target is that the computer (with help from sensors) is shooting for, that ratio is incorrect when we start adding more ethanol. Lower target ratio.

Regarding your comment on 10%, I'm pretty sure what you said is correct for our 87 octane offerred here...could have anywhere from zero to 9.9% ethanol (and does not have an ethanol sticker on the pump). But I was referring to 89 and 91 which is stickered as containing ethanol. That means it contains at least 10%, my understanding is it's close to that but could be more. The premium/91 used to be under 10% and not stickered, where now almost all premium contains 10%+. I'm ok with that for the car, not so much for motorcycles and other small engines.

Minnesota has had higher % of ethanol (20%?) for years at most pumps.

As a side note, at least where I am located, the fuel wholesaler receives a blender's premium (per gallon) which is a government incentive to utilize ethanol...so it is in their best interest to (within reasonable limits) blend in, and sell as much ethanol as possible. This is at least part of the reason why blends with more ethanol, cost less at the pump (there may be tax incentives as well). There is a common misconception that this extra $$ goes to the ethanol plant.
 
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