My user manual states to fill up with a tank of regular gasoline at oil change time when normally running E85. I can't find anywhere on the internet why this is stated in the user manual. Any ideas?

 

E85 burns so clean and has less lubricating properties than regular gas. That note is meant if you run E85 exclusively, I do.
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I've been running it for 5 tanks now and want to stay with it. I found a good high turnover source with great pricing and my truck runs much better on it. But I don't understand why it's recommended to switch back to regular fuel once every oil change.

 

I must be using invisible ink again.
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So it needs one tank of regular gas every 5,000 miles because of its lubrication properties. Doesn't seem like it will help much. So really, these are not full FFV capable trucks. Seems like it should have a lubricating additive every tank full of E85 to properly protect the truck.

 

They are full FFV trucks in every sense, I was making a SWAG.
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I burn E85 exclusively as of late as it's so much cheaper than regular gas($1.79 vs $2.79 for regular gas). My brother(who is a high-performance engine builder and E85 guru) says to use the Lucas Fuel Treatment in every tank. I buy it by the gallon at my local farm/fleet store and add accordingly when I fill up. Lucas recommends 2-3 oz per 10 gallons of fuel. I am no mechanic or expert. I'm just going strictly off what my brother recommends who is pretty good with engines and knows his E85. Here is a link to the product I'm talking about.

https://lucasoil.com/products/fuel-t...fuel-treatment

 

Have you checked its cost per mile vs. E10 or E0? (Cost/gal) / (MPG) = Cost/mile If it costs more to go a mile, it's not cheaper.

 

It's been calculated a 30% less cost amount makes it worthwhile financially. $1/g less is a little more than 30% savings.

I however couldn't care less about the savings, I like the enhanced power coupled with my custom race tune as well as a smoother running engine. On reg gas I can tell the engine's running just a little bit, typical engine quiver. Not so with E85. Engine runs so smooth I only know it's running at idle by watching the tach.

With that said I must run 93 octane premium fuel due to the aforementioned custom tune thus the savings is even greater when comparing the two fuels.
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I run mine stock. I know the prior gen F150 advertised sizeable gains in HP and torque running E85 for the 5.0 because the truck's computer adjusted timing for it. I cannot find the number for 2015+ trucks though, but it's very clear my truck is producing more just running E85.

on the pump I buy E85 from it states can contain 51% to 83% ethanol. I've only been running 10% less fuel economy than regular gas so I suspect the pump for E85 is closer to 50% where I'm buying and it's 35% cheaper than gas.

my upper engine is louder on it. Some knocking and ticking. Added marvel mystery oil to it and quieted right down. Then I noticed the marvel mystery oil said not for use in fuels exceeding 30% ethanol. Saw the same kind of note on Lucas products. So I'm at a loss as to what additive to use.

but I want to use E85 for how well my engine runs on it. It's really pepped it up. Just don't want any long term damage. That's why I was curious about the strange note in the user manual.