smlranger

I just got my new 2017 GT convertible. This is my third Mustang...first was a 1965 ragtop with the 289, the second was a 1993 GT and now the 2017 GT. Wow, what a car.

So my fuel question. Reviews that I read before buying the car said both the 5.0 Coyote and the 4 cyl Ecoboost required premium fuel. However, the owners manual for my 5.0 GT says 87 octane is recommended.

I'm still on the dealer-provided first tank of fuel and I have no idea what they put in it.

JimC

All you need is 87 octane. the car is tuned for it.

However, the knock sensors will let you do premium and pick up a few horsepower. Will you actually notice the 15 or so extra flywheel horsepower? If you really want to feel a difference then you need a tune to adjust everything. You need premium to get the full horsepower out of the engine, but that doesn't do anything for any other parameters or the shifting on the automatic.

Otherwise, you can run 87 octane with no issues.

And no, premium doesn't "run cleaner". That theory has been tested multiple times.

69mach1377

Use a top tier fuel if you can, also.

IB Cristina

I'm with Jim here. You're wasting money by filling up with premium when it isn't recommended. Premium doesn't get you any significant increase in horsepower or fuel economy, or any significant decrease in emissions.

bluebeastsrt

Tune it if you want more power from 93. It'll also take the slack out of weak transmission shifts.

Roadie1600

New owner here. I'm due to pick up my first ever Mustang this afternoon. It's a 2017 GT Premium. Sorta like Christmas morning with anticipation.