P.S. Here are some notes on my E85 experiences from last winter:
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I have run about 3 tanks of E85 through my Raptor.
Cold Starting
I live in a fairly mild climate compared to some of you. "Cold" is in the 30's. (Fahrenheit).
On gasoline, my Raptor initially idles around 1000 rpm for a few seconds but pretty quickly the idle drops to about 500-600 rpm.
On an E85 cold start, the engine rpm jumps up to 1750 rpm. About the time the gauges do their sweep thing, the idle rpm starts to drop. Usually a few seconds after that the rpm is down to 1000. (I wait until this point before putting it into gear... the wait can be mildly annoying.)
(---ADDED NOTE: now that the weather is warm, a higher idle on E85 when cold is all but unnoticeable---)
When warmed up, both fuels idle smoothly at a rock solid 500 rpm. (A/C off)
Power
Here is where E85 shines. The engine definitely feels like it pulls stronger off idle and in the normal driving rpm range when running E85. It's not a night and day difference, but you can feel some extra "punch" and it makes the Raptor more fun to drive imho. At higher rpm, it's hard to tell any difference by the SOP method (seat of pants).
Mileage/Economy
I was actually expecting worse results here. E85 costs about 17% less in my area than 87. I've heard that E85 gets about 25% worse mileage. My test methods are far from scientific but after three tanks on E85 over the same routes (mostly the commute to work), the mileage is averaging about 22% worse on E85 vs 87.
There is one other thing I'd like to mention here. The E85 pumps at the station near me have a big red sticker on them that states "contains a minimum of 70% ethanol". So it is very possible the E85 I've been using is not really E85 but something closer to E70. This could explain why the mileage wasn't as bad as expected.
Conclusion
E85 is a safe and easy way to get a fun little extra boost from the 5.4l. The drawbacks are that you have to fill up more often and the warm up idle thing. (I expect the cold idle could be a bigger issue in colder climates)
While E85 costs less per gallon, you don't go as far on each gallon. This makes using E85 slightly more expensive than using 87. However, gas prices here have started to climb in the last couple of days and E85 was 20% cheaper than 87 when I filled up today. I expect E85 prices will go up soon too but if the cost gap between E85 and 87 continues to widen, E85 might actually make sense from a cost per mile standpoint.
