Chromeshadow

I think it was R&T that did a dyno run on the 3.7 and got 7 more hp on 93 than on 87. I've run several tanks of both on mine and did not feel any difference or see any difference in mileage. I usually run the mid grade gas on both the 3.7 Mustang and the 5.0 F150.

Callinectes

I fill up once a week. I figure the 93 costs me $3.20 a tank over 87. I understand that the 87 actually burns hotter. More heat=more wear and tear. For me, it's worth $12.80 a month.

The Sheriff

That's very interesting & good to know. Where did you get this information?

Mishri

There were some reports of people who once they put 87 in, it would never go advance the timing again for higher octane gas (This was with 2011, 2012, I don't know if they fixed it). Luckily I've only ever put 91 in (93 isn't available here, we have 85.5, 88, and 91)

BrazenStang

If you went to the doctor and he/she "recommended" that you stop eating fast food and eat healthy, would you listen? Ford engineers recommend premium fuel for a reason because it is better for a high performance engine.

Personally, I choose to follow my doctor's recommendations and I also follow the fuel recommendations for my car. Its your choice, but in the end they are the experts. Is it worth the few dollars per fill-up to skimp on gasoline?

Troponin

Most dealerships will put 87 in cars if they can get away with it, so don't bet on it never having 87 put in it. I think the GT500 is the only car they actually fill up with premium.

HRDWRK

Ford is recommending 87 in their manual for 5.0 engine! That was the cause of confusion.

AJ06GT

That's because the cars are tuned for 87. 87 will have absolutely no adverse effect on your engine. Traditionally changing your octane does absolutely nothing for performance or gas mileage, but with as complex as engines are getting and automatically adjusting, I've heard it rumored that the Coyote engines can actually get a gain from 93, even without a tune, but I've yet to see any official source confirm this. A dyno run can easily fluctuate a few HP between each run, so that's not really the best indication either since you're going to be talking a very small difference without a real tune. I'd have to see some kind of hard evidence to prove that 93 actually does give you a power boost to believe it though. It is a difference of less than $3 a tank though if you do want to run it, but I highly doubt you'd notice a difference if you just used 87.

Troponin

I am pretty sure it's in the Ford owner's manual, but even on the Ford website, all off their hp claims are with premium. So yes, Ford has confirmed the car will adjust the timing to run regular in it safely, but performs best with premium.

http://www.ford.com/cars/mustang/specifications/engine/

AJ06GT

Oh, well then yeah, so with premium it's going to tune up. I'd always heard people talk about it but no one had ever posted a link like that before. I'd probably pay the extra $3 or so a tank, but the difference is probably barely noticeable. You'd still want a specific 93 tune to really get everything out of it otherwise paying for just 87 will still be fine which is why the manual states that.