My 2013 GT should be arriving any day now. I looked up the owner's manual online and it says 87 octane is recommended. The performance figures show more horsepower and torque at 91 octane. In my area we also have 93 and 94 octane available. Understanding somewhat that higher octane prevents premature detonation of the air/fuel mixture (although today's cars will adjust their timing to compensate), thus providing more power by allowing the detonation to occur at the optimum time, I'm wondering if there is any real difference between 91, 93, and 94 octane? 91 octane is a bit cheaper, and I'd like to use it if 93 and 94 don't make a difference. This of course is assuming I stay with the stock tune. If I start making mods, I understand that I may need to change the fuel to optimize the power gains.

 

I used 87 till I installed my tune and cold air intake than I started to use 93 only because bama recommended it but I ain't complaining.. Running stronger to me

 

I'd also like to know, if the stock tune will see any benefit from 94 over 91.

 

the higher octant the better in my book runs better and get more power, reduces knocking and if your complaining about 3 bucks or so per tank then i think a v8 wasn't the right choice for you

 

This is very subjective though. The timing will adjust to lower octane fuel to prevent knocking. Saying that "the higher octane the better in your book" isn't very scientific. What I'm asking is, are there any performance gains over 91 octane. I'm not complaining about the price of gas, but if there is no benefit to using 93 or 94, then why throw away money?

 

10 hp is what you get and it's up to you to decide if it's worth it.

 

I would use minimum of 91, never used anything less than 92 in mine but I try to stick with 93.

Detonation is bad period. Detonation is what causes bad and blown motors and burnt up piston rings you hear about. Combustion, or more specifically, deflagration is what you want to occur in the cylinders.

 

Between 91 and 93? Is there some website where I can confirm this? Any little bit of extra power is worth it to me, but I want to make sure it's real if I'm going to be paying for it.

 

10 hp is he difference between 87 and 91

 

And yes, go on any ford website or anything that had data on coyote mustang and it will say this

 

Between 87 and 91/93

 

Actually, it talks about the difference between 87 and 91, not 91 and 93 which was my original question. I just want to know if going over 91 provides any measurable gain or other advantage. I'm looking for someone to point me to a website that says for a fact 93 prevents detonation better than 91, or 93 provides 5 more hp than 91, or something similar. If nobody knows of a source of this information, there either isn't any real advantage, or I might have to ask Ford directly what the facts are.

Thanks!

 

Octane has to do with the number of 8 carbon hydrocarbons (also known as octane) in gasoline. I'm not completely sure how octane is measured but I do know that the higher the octane the more 8 carbon hydrocarbons there are. Now an octane molecule requires more energy to burn than 7 carbon (septanes) and 6 carbon (hexanes) hydrocarbons. Therefore any fuel with more octane molecules will require more energy and will have more resistance to burning prematurely (detonating, or an uncontrolled explosion in the cylinder), and deflagration will occur (burning more slowly and controlled as opposed to exploding). So naturally any fuel with more octane molecules will be more resistant to detonation

 

Not with a stock tune. Your PCM will adjust timing down a bit for 87 but won't compensate for 93+.

 

Use 91 or higher to get the maximum performance out of your car according to the owners manual. 10 hp is worth the extra 3 bucks.




Octane recommendations (5.0L V8 engine)
Your vehicle will run normally on 87 octane regular fuel without
damaging the engine, but premium fuel with an octane rating of 91
(R+M)/2 or higher is recommended for best overall performance.

 

Does anyone know the answer to his original question?.. I don't know, only use 87

Is there a difference in performance between using 91 & 93 octane?

 

No..

 

Ideally you want no more octane then your engine needs to make max power. Any octane higher then that amount will not burn completely and can actually be detrimental to peak horsepower numbers. I'd say that 91 would abbé all you would need to make max power stock but with a tune that calls for 93 I'd stick with that. Premium fuel is not only higher in octane (obviously) then the lesser grades but it also contains a different detergent package then 87 octane. At all of our stations (we have 11) the Midgrade is actually blended 87 and 93 and it's done internally at the pump. So with Midgrade your getting some of the detergent package of the premium fuel. Hope that cleared it up a bit for you.

 

I used 87 for the first tank or 2 then switched to 93. I may use 91 and see how that is. From what I hear 91 is pretty much the highest you need to go for max output on a stock tune

 

Ultimately your 100% correct.
I have a tune and I run 93 exclusively. I also run 100% gas (no ethanol) but that's not even available in most places. If you are stock though you won't see any performance gain over 91 octane.

A tank of premium once every ten tanks wouldn't be a bad idea on a stock car but it's certainly not required.