I might have to venture to JM this summer, but my car is running fine now. I've also been putting in 2 gallons e85 with non oxy 91 (this comes to 10-12% etoh ~92-93 octane). No idea for sure if fuel (condensation?) was an issue at or below 5F. Now that temps are warmer, no issues at all. My mpg hasn't been stellar, but not bad - 21-24 mpg average with the etoh mix. I'd like to consider an e85 conversion this summer but I'd like to make sure I'm all good mechanically. Which reminds me, I haven't retried a compression test.
His logic makes sense. It's actually an approach I took while tuning. Pump oxygenated 91 could be a lower octane than 91 plus a splash of ethanol to" bring it up to" 91. The idea is it makes the fuel behave like 93. The problem is that there's not much proof on if stations are doing that or if they are actually checking 91 and then mixing/cutting 10% ethanol in. Your process is also a bit of a gamble because e85 can range 50-80%. Rarely do you find solid 85%. On the flip side, You also might not get a good mix in the tank and you might see swaying fuel trims. That's the massive appeal of a flex sensor, no worries on what ethanol % hits the injectors because the ecus already accounted for it. Without a sensor I'd opt for what ever the pump 91 ends up being instead of measuring out non oxy and corn.
Doing it this way I can promise you that exactly what you said huge swinging fuel trims will happen. I know this because I have done exactly what he has done and seen the swinging fuel trims 1st hand before.
You could argue that he took a safe approach to it... It gave him results that he should analyze and not check it off as a fix. There's more to ethanol than volume displament math. For example, I've noticed fuel flow seems to change with temperature more drastically with ethanol vs pump gas. I'd take logs on the mix you've made, then go back to pump and see if you can see any changes in the logs. Or don't. You are an adult and I can't make you do anything.
Also, absolutely do a compression test before swapping to e85. You don't really want ethanol blowby, as @JasonoJordan and I found out last weekend.
I've done the calculations with e60 to e85, 1 to 2 gallons per 13-15 gallon fill up. I have a good idea of what I'm doing. I have a minor in chemistry FWIW. I also look at my LTFT all the time - usually within 0 to 5%, (7% at most) in all ranges (ABCD). and I don't go into boost or even OL much. I won't if LTFT is negative. I'll be adding dual catch cans before e85, bigger injectors, wideband, etc. That is if I even go through with it. Anyway, it seems to be running fine since it's not 5F or colder outside.
