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There's no right and wrong answer, because every person will have a different experience.

Even with dyno tuning, variations in ambient air temperature and humidity, as well as altitude will affect mileage and performance.

Each person's driving habits are different as well. I've put 8,000 miles on my 2012, I'd guess probably 60% city and 40% highway. I've NEVER seen more than 35mpg, even on trips that were 100% highway, driving with the cruise control set the entire trip.

*I do have a heavy foot, so this is most likely my fault.

I tried 93 octane for 3 tanks of fuel and did NOT notice any improvement over 87.

After that, I switched back to 87 and removed the cover on the air intake.
Despite higher intake air temps, I did see an average gain of about 4mpg over 8 consecutive tanks of 87 octane, as well as better throttle response in the low end. Throttle response is better in the high end also, but not as dramatic a change as in low end. The engine stumbles less now as well, as long as I can get that stupid DCT transmission to downshift appropriately.

Next, I plan on trying another 3 tanks of 93 octane with the cover removed.
 

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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).

That's what I understood from it. Unless your racing your Focus in the Daytona 500 I think I'll stick with 87. I average 34 mpg between city and highway using 87. These engines werent designed for high octane fuel like a higher performance engine would be, hence the manual stating to use 87. My fathers Acura states to use 93... He's not out there looking for racing fuel
 

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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).
I think if that is what they meant to say they would have written just as you did, but they didn't. To me it is two separate thoughts, Don't use less than 87 octane, and they told you where that might be encountered, and premium fuel will provide an increase in performance. Simple. Plus my experience using shell V-Power has shown me, that just as in the video, oh yea, did anyone watch the video, I am getting an increase in performance using premium.
 

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This isn't rocket surgery folks

When the owner's manual says "Premium fuel will provide increased performance" under the heading "Octane recommendations" it sounds completely unambiguous and unqualified to me.
 

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I think if that is what they meant to say they would have written just as you did, but they didn't. To me it is two separate thoughts, Don't use less than 87 octane, and they told you where that might be encountered, and premium fuel will provide an increase in performance. Simple. Plus my experience using shell V-Power has shown me, that just as in the video, oh yea, did anyone watch the video, I am getting an increase in performance using premium.
Well from a proper English stand point, if the part about the higher octane was unrelated to the prior sentence, than I would think it would have had a separate spaced line in the text. Just my 2 cents.
 

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Well from a proper English stand point, if the part about the higher octane was unrelated to the prior sentence, than I would think it would have had a separate spaced line in the text. Just my 2 cents.
I see your point, but this is not a novel, just an owners manual.
 

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Hum, an increase in performance does not mean I can go further down the road on the same gallon of gas????? OK
Define performance, are you referring to better acceleration, engine response. When your driving 65mph, which performance characteristic helps increase your mpg.

My understanding of Octane: It will provided more power and not more mpg. I have never seen any real MPG increase in my 30 years of driving. Too many environmental variables can effect this too. Plus the FF is built for 87 octane so performance maybe, MPG not so much. Yes some people are using 93, but most because they have Exhaust, SRI or CAI. It will be debated forever. Just my 2 cents... Not saying you are wrong either..
 

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The fact that the car has a compression ratio of 12:1 would favor higher octane gas. The smarts in modern cars and the ability to dynamically change valve and ignition timing and other parameters as well permit you to use lower octane gas but 12:1 would still prefer higher octane.

I can imagine a dual performance benefit of slightly more power AND slightly better mpg, but just how much better the mpg is I can't say and short of a true scientific series of tests it would be very difficult to see that difference unless the differences is larger than about 5% percent or about 1.75mpg.

I'd put the difference in price between the highest octane gas versus the lowest octane gas to be about 7%, and the difference between mid and high octane being about 4%. So, if the lowest octane is below 87 than the real difference would be between mid and high so roughly 4%. If the improvement in gas mileage is greater than 4% then it would be cheaper to use high octane versus mid octane.

Those of use living in mountain regions usually see the low octane being 85 or less than 87 so we need to go with either mid grade or premium gas.


Brian
 

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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).
Huh - that's an interesting take, and I actually sort of think I agree with you.

At first I thought it was pretty clear that it meant simply what it said, but in context it seems to be saying that premium fuel will give better performance than sub-87 octane fuel labelled as Regular, not better performance in general.

But hey, I think people should put in whatever fuel makes them happy. My BMW asks for 91, so that's what I use (actually I use 93 because I can't find 91 here). I think when I get the Focus I'll use 87, because IMO that's what it seems to be asking for.
 

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Well from a proper English stand point, if the part about the higher octane was unrelated to the prior sentence, than I would think it would have had a separate spaced line in the text. Just my 2 cents.
If you're going to make a point about proper English you should probably start with proper grammar. just sayin
 

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If you're going to make a point about proper English you should probably start with proper grammar. just sayin
You type that and then make a comment about my grammar? LOL

And yes, that was supposed to be then, not than.
 

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Actually the term FFV is including e85, not just 87-93 octanes. Otherwise everything would be a FFV.
Yes, I understand what FFV means. You do realize that e85 has a higher octane rating than 93 though, right? That is why I stated what I did.
 

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I watched the YouTube video and here's what I got from it....

The cars that require higher octane fuel get better performance with higher octane fuel than with lower octane fuel.


I wouldn't place a Ford focus in the same performance catagory as a gti or wrx
 

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If you look at the fine print in the latest Taurus SHO commercials it states that to get the full 365 hp you need to run premium fuel. So if ford is programming the PCM on the SHO to sense different octanes and adjust power output accordingly, then they are probably doing it on our focii also.
 
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