Cheap gas is not worth the risk.  Remember this post originated from buying cheap gas and a check engine light. That should be a red flag for all of us. Thank you for the post. It just enforces my belief that good top tier high octane fuel is beneficial. Maybe not such a big deal for a non-turbocharged engine???

OK, that's good. How about the second part of the question?

It's a motorcraft alternator 

Hey, use whatever you want for fuel.  Your money.  Your car.   You are only running an SEL.  STBeast and myself are running an ST.  Clearly states in the manual for premium fuel, not the cheapest we can find. I would never use cheap fuel, ie; 87 octane in a turbocharged car unless I was desperate and there was nothing else available, and only then just enough to get me to the next station.   Since you apparently used an unknown station, or one you would not normally use, may very well have gotten a bad tank of contaminated fuel.

A lot of either wrong manuals in your vehicles infotainment system, or...who knows. Creative interpretation?   E15 is okay for 2001 and newer vehicles, some are grand fathered in due to the EPA testing them.   Every Ford Edge. 2013 or newer, in the owners manual, states that not more than 15% ethanol. You know what is not more than 15%???? 15%.   Sure, if I had bottomless pockets, or didn't drive 22,000 miles a year, or didn't have a appliance CUV, sure, always 91/93 pure gas 0% ethanol. Especially if it sat with a tank of gas for more than a few days, which mine doesn't. https://www.fordservicecontent.com/Ford_Content/vdirsnet/OwnerManual/Home/Content?variantid=9611&languageCode=en&countryCode=USA&moidRef=G2126645&Uid=G2170137&ProcUid=G2134123&userMarket=usa&div=f&vFilteringEnabled=False&buildtype=we

The Edge is not a FlexFuel vehicle, hence not designed to run on anything more than 10% ethanol.   IIRC, 93 Octane seems to be more of an East Coast thing, ie; more prevalent than on the West Coast.

Just revisiting this - fairly risky to drain the coolant with it at normal operating temperature and even if that was done, it would be well below operating temperature with the new cold coolant just added and would take longer than 10 minutes to get back up to operating temperature.

I have done two drain-fills on my 2017 Sport.   The fact that the new spec Ford coolant is compatible with the old spec there's no issue with not purging all the old coolant and I didn't purge the system on each occasion - the first time it the fluid in the reservoir didn't look anything like the new color, and with the second drain-fill its closer to the new color.   Maybe next time I'll purge it with distilled water before refilling.

Unfortunately in California we only have 91 octane. I have been running it since new. I think for the ST premium is the only fuel anybody should use.  My owner's manual says the vehicle is designed to run on 10 percent ethanol max. Mine is a 2024 so I cannot imagine any Edges made before mine are designed to exceed that limit. 

I stated concentrated, ie; non-diluted, because when you flush the system as described, you will be left with water still in your system.  By using the concentrate, you will be close to a 50 / 50 mix.   BTW, the concentrate is cheaper than the 50/50 mix from the supply store and you are paying for water. As 1004ron said, I also buy the concentrate and dilute on my own