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I tried both 92 and 89, and settled on 89. Smoother at low speeds, a little better mileage, and a little more power. The 92 wasn't better than the 89 so I went with the cheaper choice.

I know this is subjective, but I notice a difference.
 

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If your engine is not knocking and/or pinging there will be no difference in using 87 Vs 93 octane. The only thing the higher octane would do is reduce a tendancy for pre-detonation (knocking/pinging). The engine is designed/engineered to use 87, anything more would be a waste of money.
The 2.0L EcoBoost (turbocharged) engine that is used in the 2013 Escape (and other vehicles) is also designed to use regular unleaded (87).

Are you certain that there would be no benefit to using higher octane fuel in an engine that was designed for 87?
 

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If your engine is not knocking and/or pinging there will be no difference in using 87 Vs 93 octane. The only thing the higher octane would do is reduce a tendancy for pre-detonation (knocking/pinging). The engine is designed/engineered to use 87, anything more would be a waste of money.
Are you certain that there would be no benefit to using higher octane fuel in an engine that was designed for 87?
Good question...

Especially since pg 354 of the Owners manual says "Premium fuel will provide improved performance."
 

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If your engine is not knocking and/or pinging there will be no difference in using 87 Vs 93 octane. The only thing the higher octane would do is reduce a tendancy for pre-detonation (knocking/pinging). The engine is designed/engineered to use 87, anything more would be a waste of money.
The owners manual is a good place to look for information, as posted earlier. And once again here is a link to a possibly informative video on the subject.[?|]

http://www.youtube.com/watch?v=gQghB4asSnI
 

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Just wanted to jump in and put some info into this debate. If you look in your owners manual in the "maintenance" section approx page 330ish it says "Some stations offer fuels posted as 'Regular' with an octane rating below 87, particulary in high altitude areas. Fuels with octane levels below 87 are not recommended. Premium fuel WILL provide improved performance."
 

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If you look in your owners manual in the "maintenance" section approx page 330ish it says "Some stations offer fuels posted as 'Regular' with an octane rating below 87, particulary in high altitude areas. Fuels with octane levels below 87 are not recommended. Premium fuel WILL provide improved performance."
This was already stated several times in this thread.
 

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This really isn't rocket science. The higher the octane, the slower the burn rate. There is no "performance" gained from higher octane fuel. Any engine will run it's best on the lowest octane fuel that can be safely run. If you have a NEED for higher octane, then you will see a gain in performance, but it's from the timing, compression, boost, etc....not the fuel. Higher octane fuel just slows the burn down so that the burn happens a bit later in the cycle. If you have a motor with high cylinder pressures or temps (i.e. boost, high compression) then you need the burn to occur later otherwise you can get detonation.

Nobody with a properly running engine should be legitimately "gaining" fuel mileage or performance from higher octane than factory recommended. If they did, then that particular engine needed it in the first place.
 

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This really isn't rocket science. The higher the octane, the slower the burn rate. There is no "performance" gained from higher octane fuel. Any engine will run it's best on the lowest octane fuel that can be safely run. If you have a NEED for higher octane, then you will see a gain in performance, but it's from the timing, compression, boost, etc....not the fuel. Higher octane fuel just slows the burn down so that the burn happens a bit later in the cycle. If you have a motor with high cylinder pressures or temps (i.e. boost, high compression) then you need the burn to occur later otherwise you can get detonation.

Nobody with a properly running engine should be legitimately "gaining" fuel mileage or performance from higher octane than factory recommended. If they did, then that particular engine needed it in the first place.
That's nonsense.

You clearly have no understanding about the engine management.
The PCM is more "intelligent" than you can probably imagine.
 

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So, rather than speculation, the only way to solve this is through dyno testing in both 87 and 93 octane modes, right? I haven't seen that one yet. If I've missed something, please let me know.

FWIW, I've been running 93 for a while now, and I'm averaging a little over 32 MPG in mostly around town driving. One place where I notice a difference is on uphill climbs, where the 93 clearly allows the engine to pull better.
 

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Filled up with Shell V Power (i think 93 octane) and pulled 41 mpg on a 50 mile trip today. Usually average 36 at best, going 65 mph... I had the cruise set at 75 this time around.

Call it what you will, I think I'll stick with what works.
 

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Nonsense.

You clearly have no understanding about the engine management.
You're right, my 15+ years of custom dyno tuning, engine management calibration, and drivability diagnostics have taught me nothing about octane and fuels [rofl]
 

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You're right, my 15+ years of custom dyno tuning, engine management calibration, and drivability diagnostics have taught me nothing about octane and fuels [rofl]
That doesn't matter.

You clearly do not understand the engine management of the 2012 Focus, therefore your generalizations about octane do not apply.
 

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I apologize if that had already been stated. I was reading through the owners manual for the oil capacity and came across that in my reading. Any who those who prefer to see physical evidence here's a pic out of the owners manual for your viewing pleasure!

 

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You clearly do not understand the engine management of the 2012 Focus, therefore your generalizations about octane do not apply.
I don't understand why so many people have a hard time wrapping their heads around VVT.

I apologize if that had already been stated. I was reading through the owners manual for the oil capacity and came across that in my reading. Any who those who prefer to see physical evidence here's a pic out of the owners manual for your viewing pleasure!

You mean the part that states; "Premium fuel will provide improved performance"?

I'm staying out of this one. All I know is since I got my car 11,500 and 10.5 months ago I've only for the most part used E0 91 octane. If E0 isn't available I just use 87 - which is rare. If I have to use 87 I always notice a decrease in fuel economy and SOTP performance.
 

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So, rather than speculation, the only way to solve this is through dyno testing in both 87 and 93 octane modes, right? I haven't seen that one yet. If I've missed something, please let me know.
Once again for those that missed it, or just didn't watch it. They don't use a Focus, but I believe the Focus has the similar sophisticated engine management, TI-VCT, that the Subaru and the VW have.

http://www.youtube.com/watch?v=gQghB4asSnI
 

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I apologize if that had already been stated. I was reading through the owners manual for the oil capacity and came across that in my reading. Any who those who prefer to see physical evidence here's a pic out of the owners manual for your viewing pleasure!

The way I read that verbage in the manual, is that it means in areas where regular is considered lower than 87 octane, to use fuels labeled premium for better performance (especially in high altitude areas).
 
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