I have a 2014 EC Boost F150, from what I've read it has 10:1
Compression. My question is this enough compression to
Completely burn 91 octane fuel?
I read a what seemed like dissertation on high octane fuel
From a pretro/Chem engineer explaining why you should
Not use high octane fuel in any engine that wasn't a high
Compression engine capable of completely igniting/burning
The fuel charge.
Sooooo is the EB Boost engine capable of taking advantage
of the power gain associated with higher 91 octane
Fuel?

 

I run 91 just because of my tune. The eco will do fine on any fuel you out in it.

 

No disrespect intended but I was hoping for a few more details relative to my questions
i.e. Confirm 10:1 compression ratio in 14 EC Boost engine.
Is 10:1 capable of complete burn of 91 octane fuel etc.
Will 91 octane fuel improve performance in a stock configuration?
Any engine builders out there... where is Jack Roush when you need him?????

 

Although the Ecoboosts will run on 87 octane, they will make maximum power and torque on 91 (or even 94, if you can get it). This is because they will advance timing to the point of engine knock, which will occur later (more timing advance) with higher octane. Having said this, my "seat of the pants" assessment barely noticed any increase in pull or acceleration when I alternately ran 87 versus 91 with my usual commuting to work mix of city and highway driving. I got slightly better fuel mileage with premium fuel. The minimally improved mileage and acceleration did not justify the added cost of a fill-up with premium, in my opinion.

In Europe, the Fiesta ST Ecoboost is rated by Ford as having about 7% more HP with 94 vs. 91 octane. I cannot find any data for North America, but the results are probably similar with the 3.5 EB running 91 versus 87.

 

Yes 10:1 is plenty to effectively utilize 91 octane fuel-even without boost- and yes you will get slightly better power and fuel economy numbers because the engine management system is programmed to constantly seek optimum spark timing. Basically it's constantly feeling for the edge of detonation. The petro/chem engineer was correct about excessively high octane in an engine that can't properly utilize it due to inadequate compression. You'll get a prolonged dull burn that results in high cylinder head temps and high exhaust gas temps, which puts the exhaust valves at risk. You can "fudge" the effects of excess octane to a degree by advancing the timing slightly, but if you go too far you start reaching peak cylinder pressure too close to TDC and power output is reduced and internal engine stresses go up considerably. With excessively high octane, you often won't get detonation to let you know the engine is getting out of its happy place-for lack of a better term. Ideally you want to reach peak cylinder pressure at about 20 deg. past TDC. There are variables such as rod length, bore to stroke ratio and reciprocating mass to consider, but 20 deg. is a good ballpark.

 

Yes, your truck can take advantage of 91 octane. But I don’t think you’ll notice a difference under normal daily driving, so I don’t believe the fuel cost increase is worth it. The exception is if you’re towing a longer distance or through mountains, then it’s probably worth putting the higher grade in. But if you really want to run 91 the entire time, you certainly won’t hurt anything.

I ran a couple tanks of each grade through my EB when I first got it. I never noticed a difference and fuel economy stayed the same. It wasn’t until I added a tuner that I noticed differences. My truck tuned on 87 was stronger than my truck stock on 93 octane.

 

Did you look at prior posts on this subject before posting? Might be why you got so few responses.

As noted in your manual, your Ecoboost can benefit from 91 octane when it's under load (i.e. towing). Otherwise, you're likely to see little advantage, and definitely not an economic advantage (i.e. spend more, get more MPG or HP). Discussed many times on the forum.

 

I currently run 89 in mine. We were told to use 87 because there would be no advantage in every day running but 89 gives me almost 2mpg more on average then 87. Cost is essentially a wash. At current prices I think I am paying 1 or 2 cents more a mile.


What I find to be a much bigger factor is where you get your gas. I use our local Royal Farm because they are the cheapest for midgrade. However I lose mileage and power if I get it anyplace else. Shell seems to be the worst. I would like to find someplace that sells it with less ethanol but I think that's impossible in our area.

 

I think I've noticed a difference between gas. I typically fill up a Kroger because I get $1 off per gallon, or a local chain that's a mile from my place. But there's been a couple times I've filled up at a Sunoco station and after about a 1/4 tank I noticed that my truck felt more peppy.

 

I don't buy the +2 mpg going from 87 to 89. Not. One. Bit.