I found out,to my surprise,that E85 is 108 octane,that's higher octane than 100LL AV gas(airplane fuel) at a lean mixture,impressive and I want to try it.

 

It's fun but you burn it up quick and it's usually not much cheaper than 87. You will enjoy the performance though.

 

x2, ran it once in my 2014. gas mileage went to **** but it ran like hell

 

does E85 really make that big of a difference in performance?

 

I've put 3 tanks through mine and it definitely runs better. I experienced a 21% loss in MPG so I only buy it if the price is more than 21% lower than 87 octane. Someone correct me if I'm wrong, but I think E85 can be any ethanol content up to 85 so that efficiency loss/performance gain may vary depending on where you buy it, regional differences, etc. I've gotten all 3 tanks in mine from the same fuel station within a fairly short span of time.

 

Without tuning to accommodate the extra octane value, you won't get the best out of it. While it's cheaper than 87 the fuel economy with it will be terrible.

and yes, MCR is right. The ethanol content could be UP TO e85, but rarely is. Most guys who use e85 regularly are tuned for it, and bring their own testers to verify content.

 

I thought this was the whole point of "flex fuel", the truck has a sensor to know if it is running e85 and automatically adjust accordingly?

 

yes, it adjusts to the ethanol, but it's not going to give you the best performance from the e85. It adjusts timing to run properly on it, but it's not going to optimize performance the way a proper tune does.

 

Yes, unless you're running a tune for it, you won't get the full benefit. I had the 93PRX tune on my last 5.0, and noticed a nice gain with that. At the time, I don't think anyone was offering a tune exclusively for E85. Now that there are some out there, on my future 5.0, I plan on getting a tune for it.
What I was doing, if the cost between 93 and E85 was .70 cents or more difference, I'd use the E85 since my mileage would drop considerably on the E85, and I roughly figured it worthwhile cost wise.

 

If it is .50 cents cheaper then 87 I'll run the **** out of it. Honestly I miss running it even without a tune i could feel a difference in the truck. If i could get it .50 or more cheaper it would be ran all the time. that is the price i have figured with my truck on 33's. #makemethcheapagain i mean ethol.....