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i can run on 87. u get more power from higher octane.
if I had a ST, i would commute on 87, but if I knew on the weekend, i would doing some spirited driving, i would put a tank of 94 in
 

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What do the stock ST's use? I was unsure so I filled with with mid grade 89octane.
OCTANE RECOMMENDATIONS
Regular unleaded gasoline with a
pump (R+M)/2 octane rating of 87 is
recommended. Some stations offer
fuels posted as Regular with an
octane rating below 87, particularly
in high altitude areas. Fuels with octane levels below 87 are not
recommended. Premium fuel with an octane rating of 93 or higher will
provide improved performance and is recommended for severe duty or
high performance usage
87 octane is the minimum recommended fuel.

Premium fuel will provide improved performance.

I would not run anything below 87 octane if it was available in your area.

Personally I run my ST only on 91+ (preferably 93 octane), but it's not required.

My SE on the other hand typically gets nothing above 87 octane.
 

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Discussion Starter #4
I think I'm just going to stick with 89 or our mid grade here in the south. Isn't quite as dirty as the regular 87 and not as expensive as 93.

Thanks for the help fellas.
 

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A video of dyno runs from CJ Pony Parts with a stock ST using 87 octane, then 93 octane was done.
The output was identical (both HP and torque) up to 5,500, then a drastic cut in power and torque from 5,500 upwards with only 87 octane.
The graph has a line straight down atthe dip point.
So the engine is protecting itself at the 5,500 mark by lowering something, on the 87 diet.

link: https://www.youtube.com/watch?v=RzyBUzFumhY

So... If you never run the engine over 5,500 rpm you would not see a single bit of diffference in power.

So for a daily commute where you are not running the rpm way up, 87 gas is fine.

Curiously on my prior 2012 Focus SE, I found 93 octane made a diffeerence all around, even off idle the engine was better. But that was with 12:1 compression..

I have started using 87 octane while I am breaking in my 2 week old ST. Kinda hard to go racing in snow... LOL
 

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A video of dyno runs from CJ Pony Parts with a stock ST using 87 octane, then 93 octane was done.
The output was identical (both HP and torque) up to 5,500, then a drastic cut in power and torque from 5,500 upwards with only 87 octane.
The graph has a line straight down atthe dip point.
So the engine is protecting itself at the 5,500 mark by lowering something, on the 87 diet.

link: https://www.youtube.com/watch?v=RzyBUzFumhY

So... If you never run the engine over 5,500 rpm you would not see a single bit of diffference in power.

So for a daily commute where you are not running the rpm way up, 87 gas is fine.

Curiously on my prior 2012 Focus SE, I found 93 octane made a diffeerence all around, even off idle the engine was better. But that was with 12:1 compression..

I have started using 87 octane while I am breaking in my 2 week old ST. Kinda hard to go racing in snow... LOL


Stock 87 Octane v.s. 93 Octane From CJ Pony Parts.

From the CJ Pony parts video which clearly shows gains across the rev range from 2000 rpm on. Where do you hear that there is no power to be had before 5500 RPM?



This matches Cobbs dyno baseline for 87 v.s. 93 octane, unlike your description. The only bit that doesn't dip off at 5500 rpm is the fueling due to the engine having the octane to resist pulling timing.

The crossover point was 2500 rpm on the Cobb data, where by under 2500 the car on 87 octane makes a few more hp, but above this all the way out to redline the 93 Octane car makes a few more HP peaking at 19 HP more and only 1 lb-ft more torque (since the torque is what is targeted, not HP).

Furthermore the torque curve is still broader on 93 octane fuel than it is on 87, even stock.

I mean you won't be causing any damage, but to say it doesn't matter is a bit much.
 

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Sorry. I should have watched the video again.. I was pretty much just remembering the big cut at 5500.
I just grabbed the link without watching it again..
Hmm I guess I will also stick to 93.. (actually so far the dealer fill I bet was 87, i filled with a half tank of 93, then another half of 93 then 5 gallons to fill of 87.. I never let the tank go below 1/2 if I am anywhere near passing my fav Shell station.


So again I apologize.. at least I brought the link in..
Maybe I will remember it correctly now... [read]
 

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I just ask myself, "will $3.00 more per fill up kill me, will $5?"
 

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I just ask myself, "will $3.00 more per fill up kill me, will $5?"
Exactly. I Always wonder why some car owners will cheap out on their gas and oil, but think nothing of dropping big $$$ on an I-phone or such. A car is an expensive investment. Treat it right.
 

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Agreed, it really cost less than most think...

Avg miles -15,000
Avg mpg (my cars 2+ years avg) - 26.0
=~577 gallons
So at 0.30$ per gallon more
= 173$ per year to use premium
I am not rich but that's nothing, a lots of mods cost a lot more!
 

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Discussion Starter #14
I was more or less asking if premium would harm the engine due to the higher octane and higher combustion temp.

I don't want to do anything to harm my less than a week old ST.
 

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I was more or less asking if premium would harm the engine due to the higher octane and higher combustion temp.

I don't want to do anything to harm my less than a week old ST.
Nope. Premium is good for the St engine.
Premium is also great for the regular MK3 Focus engine....
 

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I was more or less asking if premium would harm the engine due to the higher octane and higher combustion temp.

I don't want to do anything to harm my less than a week old ST.
You would not harm the car in any way shape or form. In fact it's required to run premium fuel to get the maximum performance out of the stock calibration.

The fact that you can even consider running 87 octane on a turbocharged car is a testament to the direct injection + variable valve timing, but traditionally you could not run such an engine on anything below 91 octane.
 

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Yup - the higher "octane" fuel adds protection by being more resistant to predetonation.

("Octane" level of a fuel is a measurement of that resistance)
 

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I ran nothing but shell 93 on my 14 se
and i have done the same on my 14 st3
i will not cheap my car on oil or gas, full synthetic oil as well
 
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