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Discussion Starter #1
I have a 15 GT 5.0, six speed with no mods. Should I use regular fuel or 93 octane? thanks
 

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At the risk of possibly sounding rude, i will tell you that with no mods, run what the vehicle calls for.
 

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i know what the manual says....but is there a performance benefit from running with 93 or just more cash out the window? thanks
 

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In all of the EcoBoost engines, there is significant benefit to using 93 octane. For the 5.0, I think the main benefit to 93 might be that the engine would not pull as much timing in really warm weather. Other than that, regular is fine. You might see 1 or 1.5 mpg better year round with 93. I do, which means there probably is some very minor increase in performance.
 

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i know what the manual says....but is there a performance benefit from running with 93 or just more cash out the window? thanks
It depends.
If you are the type of person who spends countless hours researching which synthetic oil is the best for a mass-produced, production engine, then your "butt dyno" might be sensitive enough to detect the minuscule amount of power increase that could potentially be achieved, in certain meteorological conditions, by using 93 octane fuel in a factory tuned car.
If you just drive the car around, like 99% of the population, I don't think that you would be able to tell the difference between a tank full of 89, and a tank of 93 fuel.
 

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If you run octane without a tune, the newer cars will make an adjustment using the knock sensors. But for the 15 or 20 horsepower at the crank you won't really notice that much difference from 87 octane vs 93.

With a tune you will get more out of the car.
 

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You'll lose a few horsepower running the lower octane, I had a 2011 5.0 and remember reading that if would fall from around 412hp to 400 with regular gas vs premium. I don't think I could tell the difference and always used regular. I have a 2018 GT on order and will run regular if I can. From what I read they doubled the number of knock sensors in the 18 and it will pull out some timing if it hears a knock, this will cause it to lose some power but I don't think I really need 460HP for daily driving.
 

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No tune=run 87. Good tune (not bama) = run whatever octane tune you get.


I run 91 US because that's what's available here and that's what I had my custom remote tune based around.
 

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the correct answer is:

$ or HP

Check fuel mpg and to do the testing correctly have someone else fill it. Blind testing is way better than knowing and expecting results. I believe on the fuel filler door it will say what it needs. If I am correct it is Premium suggested. You'll get a bit more power with it but in CT it carries a 20-30% $ premium.
 

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I?ll echo Gairds comment on better mileage with 93. Before I modded and needed 93, I ran 87 and 93 for several tanks to get an avg mpg with similar driving just for my own interest an saw a small increase in mpg with 93. Didn?t notice any gains otherwise but I wasn?t data logging or anything either. Calculated out for price per mile to drive, the difference in price wasn?t as drastic as the different in cost at the pump. It?s still more and probably not worth it if you don?t need it though.
 

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Discussion Starter #11
I'll stick with regular for now. I haven't heard a good reason to spend the extra cash on gas. Thanks!
 

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I have read that 93 octane does not have any more energy in a gallon of gas then 87 octane, therefor you will not get anybetter mileage. The additional additaves just make the gas harder to ignite so it can withstand a higher compression without detinating. Now any gas with alachol in it does have less energy per gallon than 100% gasoline, so you would get better milage out of fuel without any alachol added.
 

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Um no the higher octane makes it harder to ignite...

Sent from my Z978 using Mustang Evolution mobile app
 

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Just use what it calls for in the manual. No point spend the $$$ on 93 unless you have a tune that requires it or are running forced induction...which requires a tune. Good luck with modding and let us know how you make out.

Ted

---------- Post added at 10:58 AM ---------- Previous post was at 10:58 AM ----------

Just use what it calls for in the manual. No point spend the $$$ on 93 unless you have a tune that requires it or are running forced induction...which requires a tune. Good luck with modding and let us know how you make out.

Ted
 

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Discussion Starter #16
Ted- thanks and I agree with not spending unnecessary money. The manual calls for regular fuel so I'll stick with that. The mod I did was new catback FlowMaster system....sounds great! I think I'm just going to enjoy the new car for a while before doing anything else. Thanks again!
 

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All of the motors in all of the Mustang's since 2011 make more power on premium than regular. They have adaptive ecus with tables that allow the car to add timing until knock is detected. The owners manual will say on the 5.0 specifically the hp rating is based on premium and you will make less power on regular even though it's fine to use.
 
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ill need to reread the manual, i dont recall it saying that, thanks!
They may have dropped it in 15+ but it was in 11-14, either way it's still true.
 
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