Making an E30 Blend

[rci3044]

The local ethanol station changed from E85 to E70. About how much E70 should I add to 91 octane premium to result in an E30 Blend?

 

[ChaneRZ]

5.5 gals. Assuming your 91 has already 10% ethanol added.

 

[rci3044]

5.5 gals. Assuming your 91 has already 10% ethanol added.

Thanks! The 91, however, is ethanol free.

 

[ChaneRZ]

Then 6.8 gals

 

[Thomby]

Then 6.8 gals

That seemed a little high to me, but here's what I got from the calculator at the bottom of this page (using 14 gallons as a fill-up). Basically start with 4 gal for 93/10%/E85, and add a gallon if you have a couple demerits (91 octane, 0% ethanol, E70). But it's not terribly sensitive so round numbers are fine:

E85 Calculator Ethanol Mix

www.morepowertuning.com

4 gal E85 / 10 gal 93 oct (10%) is E31, 96.4 octane
5 gal E85 / 9 gal 93 oct (0%) is E30, 97 octane
5 gal E70 / 9 gal 93 oct (10%) is E31, 96 octane

5 gal E85 / 9 gal 91 oct (10%) is E37, 96 octane
5 gal E70 / 9 gal 91 oct (10%) is E31, 95 octane
5 gal E70 / 9 gal 91 oct (0%) is E25, 95 octane

6 gal E70 / 8 gal 91 oct (0%) is E30, 96 octane
7 gal E70 / 7 gal 91 oct (0%) is E35, 96.5 octane

 

[ChaneRZ]

15.9 gal fuel tank

 

[Thomby]

15.9 gal fuel tank

But you're not adding that much at fill-up, right? I believe the light comes on around 14. And if I fill up at the halfway mark, it's about 7, so it's easy to just put 2 gallons of E85 and the rest premium.