Those using E30 fuel...

[KrisR]

Doing this only increases the ethanol content every time you refill to the point that it is unsafe. For example, 11 gallons of 93 Oct in the tank requires 4.133 gallons of E85 and the rest with 93 oct to make E30.
Say you refill again at 11 gallons of E30 left in the tank, you only need to refill 1.2 gallons with E85 and rest with 93 Oct to achieve E30 blend

I don't see how adding an E30 mix to a tank full of E30 fuel will make it anything more than E30, but I'll think about it some more.

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[Busser48]

Doing this only increases the ethanol content every time you refill to the point that it is unsafe. For example, 11 gallons of 93 Oct in the tank requires 4.133 gallons of E85 and the rest with 93 oct to make E30.
Say you refill again at 11 gallons of E30 left in the tank, you only need to refill 1.2 gallons with E85 and rest with 93 Oct to achieve E30 blend

I thought for our cars on empty it was 3.7 gallons of e85 and the rest 93

 

[dausmus]

Using a E85 mix calculator. ....the math and science don't lie. But to each their own.

 

[dausmus]

I don't see how adding an E30 mix to a tank full of E30 fuel will make it anything more than E30, but I'll think about it some more.

If it's already straight from the pump as e30 then yes...that's perfectly alright. If blending your own you have to get a little more technical then just sticking to a ratio. Get the E85 mix calculator app

 

[Busser48]

Using a E85 mix calculator. ....the math and science don't lie. But to each their own.

Well didn't kris state he used straight e85 in the past and though our cars would be fine running straight e85 or was that someone else post

 

[dausmus]

Can not run straight E85 with our fuel system. You need aux fueling


Edit: if you do, feel free to search for the threads "my car went ecoboom" and reserve your spot for the inevitable lol

 

[KrisR]

If it's already straight from the pump as e30 then yes...that's perfectly alright. If blending your own you have to get a little more technical then just sticking to a ratio. Get the E85 mix calculator app

I always use the website listed above as suggested to calculate what I'm adding.

 

[KrisR]

Well didn't kris state he used straight e85 in the past and though our cars would be fine running straight e85 or was that someone else post

I used it in the past in other vehicles, a lot, but never suggested it could be run straight (no mix) in an Ecoboost Mustang.

 

[Busser48]

I used it in the past in other vehicles, a lot, but never suggested it could be run straight (no mix) in an Ecoboost Mustang.

Gotcha! Just misunderstood u then

 

[KrisR]

Gotcha! Just misunderstood u then

No problem! Yes from what I've learned it would not end well!

 

[Juben]

I've refilled from half a tank of E30, but in doing so, I figured the amount of ethanol I'd need to make E30 with the available amount of room.

In theory, 1/2 a tank would be 7.75 gallons to fill it up. As such, I'd throw in 2 gallons of e85 and 5.75 gallons of 93. That'd make E29.4, which is close enough.

Is that what you meant?

If you have half a tank of E30 then throwing in 4 gallons of E85 and the rest with pump, then you'd end up with E39.4. That's waaaay too much.

 

[KrisR]

I've refilled from half a tank of E30, but in doing so, I figured the amount of ethanol I'd need to make E30 with the available amount of room.

Yes, that's basically what I do every time, as I've said. But it doesn't have to be a 1/2 tank. It can be whatever.

When you fill up, set the trip odometer/average mpg meter.

Next time you need to fill up, divide the miles driven by the average mpg on that tank. Say, for example, you've driven 226.0 miles and you've averaged 25.5mpg. Divide 226 by 25.5 and you'll get (approximately) the gallons used since you last filled up (or as you call it, the 'available amount of room), in this case 8.86 gallons.

Now, using the calculator listed elsewhere in this thread, you can figure out your ratio. It looks like a 3/8 mix (three parts E85, 8 parts 93...our 93 is actually E10 in my area) will produce E30.5 (close enough).

3/11 = .272. .272 x 8.86 = 2.41 gallons of E85 to add to the tank, and topping off the tank with around 6.45 gallons of 93 should fill it up again with E30.

No need to guess at exactly where 1/2 tank is. But everyone can have their own method, whatever works. It's just what I do.


Edit: summary, basic answer,
Determine number of gallons used, aka needed to fill the tank, using trip odo method.

Example, 11.4 gallons used.
Multiply 11.4 x .27. Add that much E85 (3.08 gallons), then top off with 91/93 or whatever is there (should take around 8.32 gallons to fill)

 

[dausmus]

Or just use "E85 Mix calculator" no math involved lol

 

[Datalux]

Couple questions:

1. Is there any benefit to blending E85 with 91 to get a 93 (E25) on a stock vehicle without a tune (since 93 isn't available in Socal)? I've read stock EB's get about 15-20 more WHP with 93 than 91.

2. If a stock EB can run anything from 87 to 93 (range of 6 octane) on the stock tune, why does e30 (~95oct) require a tune? Is it all based on the increased ethanol content vs. regular pump gas with only 10% ethanol?

 

[KrisR]

Couple questions:

1. Is there any benefit to blending E85 with 91 to get a 93 (E25) on a stock vehicle without a tune (since 93 isn't available in Socal)? I've read stock EB's get about 15-20 more WHP with 93 than 91.

2. If a stock EB can run anything from 87 to 93 (range of 6 octane) on the stock tune, why does e30 (~95oct) require a tune? Is it all based on the increased ethanol content vs. regular pump gas with only 10% ethanol?

1. I wouldn't recommend it. I'd just run the 91 or maybe enhance it with some Race Gas Additive (RGA) if you really want to. I can't imagine there's really a 15-20 more hp gain on 93 vs 91 with stock tune, but I don't know that for a fact.

2. Yes, the increased ethanol content. I guess the factory tune can accommodate up to E15 (according to the manual/gas cap) and adjust fueling slightly through the fuel trims to accommodate, but I don't know of anyone who's tried E25 or higher on an EBM on stock tune. THAT BEING SAID, I did run an E20-E25 mix on a 93 octane tune on my old Coyote 2011 car and it responded very well, fuel trims went up slightly to the 1.08 range to accommodate the increased ethanol content, but it ran really well. I'd ask around before doing that with one of these though. If it were my car, I'd try it and datalog it, but I wouldn't recommend someone else do it, if you know that I'm saying.

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