Callinectes

I used to work for a Harley dealer and I asked my service manager the same question about my bike. It's more critical with an air cooled engine of course, but heat is heat and it's an enemy.

J95SNAKE

The '13 manual states "recommended fuel--87 octane" (page 160-ish); No mention of 91/93. 8 hp isn't noticeable by the seat of your pants, but, I guess if you are drag racing you will want every horse you can get. I run 91/93 because of the compression ratio. I know its kinda old school considering the computer has the ability to sense knock. I'm just not that trusting.

Troponin

oops, i lied. It's actually 18hp, according to Ford. Ford claims 402hp at the crank with 87, and 420hp with premium. I did have a source for this, but can't find it now. It was from a source like Car and Driver

AK_Kayaker

And of course the Mustang page on the Ford website, under specs, and then the engine tab, states HP and TQ figures are with Premium fuel, except the V-6.
Then lower on the page it has recommended fuel, V-6 Unleaded Regular, GT Unleaded Premium, and the GT500 also Unleaded Premium.
So which is right the owners manual, or the Website, maybe the Ford rep could check on this for us, for me I'll stick with one less fancy coffee a week and use Premium.
I think more important is to always use a top tier fuel, I like Chevron, as Techron is the one additive most all experts will agree works, and does no harm.

Troponin

They are both technically right. It's recommended to use 87 at a minimum, but if you want full performance, you need premium. If someone isn't worried about performance and just wants fuel savings, then go with 87. If you're a car fanatic, like most of us, you will want premium for the performance.

One thing to remember though. Like all systems that fluctuate timing based on A/F ratio, it can take an entire tank of fuel, or longer, to completely adjust. At least, that's how it was a few years ago. It might be a little better, but regardless, the change is not instant.

P51C

I've made 439 fwhp on 91 octane fuel, with a mild Ford racing tune that asks for 91 minimum, no other power mods. I ran 87 on the car when it was stock tune to try it and it was no problem. The car has so much power for around town, it wasn't really detectable. I think you'd want a little more octane headroom if you were planning on racing the car; it does soften up a tiny bit when it gets warm or the DA goes up, like all n/a engines.

Just buy quality gas, whatever you choose. Off brands are ofen blended and won't necessarily meet the rating. 87 ends up being more like 85, etc. This is an 11.1 compression engine so, quality fuel is needed.

Sniperfox

I have opted for 93 octane non-ethanol fuel for mine. It's the non-ethanol fuel that is available at the "GOGAS" chain stores in our state. I figure that it's worth the extra coin to stay away from ethanol and if the octane gives some extra HP, so much the better.

BrazenStang

Well said, and I fully agree that quality gas is important. However, those who are pinching pennies and not putting 91/93 in their tank will surely go to the cheapest station around and fill up with 87.

Mishri

I'm pretty certain that it doesn't burn hotter/cooler, it just determines if it is resistant to knock/detonation

https://mn.gov/commerce/weights-and-...ctaneFacts.pdf

It costs more because it has extra refining steps. These cars have knock sensors that advance/retard timing based on if knock is detected. If you can find any credible source of information about 87 or 93 burning hotter/colder I'd like to see it. Everything I found said it burns at the same temp, it's just a difference of how resistant it is to heat sources(detonation). burning hotter/colder slower/faster are laymans terms for it. It isn't what is actually going on, if they are both achieving combustion with the same amount of fuel it's an equal heat generation(they have the same BTU).

http://www.consumerenergycenter.org/...s_premium.html



also to someone else, My dealership filled my car up with 91 (highest available here) I know because I was there when the sales person filled it up.

AK_Kayaker

Hmmmm, according to the PDF you linked, under Octane facts it states "High octane gasoline burns slower than low octane gasoline. The slow burn prevents engine knock when cylinder pressures are high.".
So by the evidence you presented it is not just a layman's term but a fact.
But should I trust anything from Minnesota's government, or any branch of the government for that matter.