jsnyng

Hey guys/gals. I've been lurking for a couple of days, but now it's time to fill up my new GT for the first time. I just bought it on Tuesday.

At no point did any of the sales people or service people tell me that I needed to run premium unleaded in the car. I went to three different dealerships before purchasing. In the owner's manual, it states something like the following which I'm paraphrasing, "If you don't like your car and want to run 87 that's fine, but grow a pair, quit your griping, and fill that beast with 91 or better." (Side note: Did anyone see the "Ford recommends BP" logo?) Anyhow, I digress.

So, is it fine for me to run 87 in the car or do I really need to run 93? There is no 91 in Georgia that I know of. Most stations have 87, 89, 93? The car won't be tracked. The car will be driven 100 miles round trip daily on weekdays. I want to get the most longevity out of this motor. Is there any down side to running 87? Lower MPG? Lower power? Engine damage?

Here's a pic of my beauty.

RAMAIR

You will be fine running lower grade fuel like 87 octane, however the computer will adjust and you will make less power maybe 15HP or so not really sure. I can't see how it can hurt the engine since the computer is designed to make the neccessary adjustments to run that grade fuel.

That being said if it were me I would just always run 93 octane but I want all the power I can get and once I do have a 2011 5.0 I plan on modding it.

JIM5.0

Don't even waste your money on 89octane. You pay more per gallon as it so works out arithmetically.
93 octane to get the advertised 412 crank HP, BUT you can run 87 octane. This will not hurt the engine; the computer will adjust the timing accordingly to prevent knocking.

The drawback: Just like Ramier said, less HP. I'm not sure, but I think you still get 400 crank HP. The engine was supposed to be designed to make no less than 400 crank HP even on 87 octane (that was one of Ford's design objectives for this engine).

VistaBlue

87 octane is perfectly fine. You likely won't even notice the difference in power. I personally run 93, but only because I can. :-P

2011CS/GT

93 is all I have bought and all I will buy. 93 has a better smell to me! Hahaha hopefuly you did not believe my last statement!

Thrashard340

What does the owners manual say word-for-word? Not ad-lib. Thanks.

eightdogsbarkin

" 93 octane for the best performance"

Thrashard340

Then that's what you should use.

JIM5.0

You can use 87 octane, and it should be okay. According to the owners manual, I quote:

"Octane recommendations:
Your vehicle is designed to use “Regular” unleaded gasoline with a pump (R+M)/2 octane rating of 87. 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"

On the part about "premium" octane (91 or 93 octane), I quote:
"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.
For Shelby GT500 octane requirements, see the Shelby GT500
Supplement."

Gene K

Actual SAE J1349 Certification Results
Premium - 416 / 394
Regular - 404 / 381

Your choice.