After much speculation, EPA fuel-economy ratings for the 2015 Ford Mustang have been released.

The Mustang is normally more notable for horsepower than fuel efficiency, but the availability of a 2.3-liter turbocharged EcoBoost four-cylinder engine on the redesigned 2015 model has changed that.

Not surprisingly, the EcoBoost is the most fuel efficient engine available, while the 3.7-liter V-6 and 5.0-liter V-8--which carry over from the 2014 Mustang with some changes--prove slightly less efficient than before.

The V-6 will be offered in base models, and for 2015 it's rated at 21 mpg combined (17 mpg city, 28 mpg highway) with the six-speed manual transmission, and 22 mpg combined (19 mpg city, 28 mpg highway) with the six-speed automatic.

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2015 Ford Mustang 50 Year Limited Edition

2015 Ford Mustang 50 Year Limited Edition

That means manual-equipped V-6 Mustangs lose two mpg in the city category, and one mpg each in the combined and highway categories, compared to the 2014 model. With the automatic, the V-6 drops one mpg in the combined category, and three mpg highway.

The EcoBoost four-cylinder will sit between the V-6 and the V-8 in the lineup, so buyers will have to pay extra for better fuel economy.

The EPA rates this engine at 26 mpg combined (22 mpg city, 31 mpg highway) with the manual transmission, and 25 mpg combined (21 mpg city, 32 mpg highway) with the automatic.

There is nothing to directly compare this new engine to, but it's worth noting that the EcoBoost is about 37 percent more efficient than the last four-cylinder Mustang engine--which also displaced 2.3-liters--but much more powerful.

Finally, there's the V-8 2015 Mustang GT. It's rated at 19 mpg combined (15 mpg city, 25 mpg highway) with the manual, and gains one mpg in the city category with the automatic.

2015 Ford Mustang 50 Year Limited Edition

2015 Ford Mustang 50 Year Limited Edition

Those figures represent decreases of one mpg highway for the manual, and two mpg city and one mpg combined for the automatic.

The decreased V-6 and V-8 fuel economy is likely due to the 2015 Mustang's heavier curb weight.

MORE: 2015 Ford Mustang: How High Will Its Gas-Mileage Ratings Go?

Compared to the 2014 model, the 2015 Mustang V-6 gains 30 pounds with the manual and 12 lbs with the automatic, while the V-8 GT gains 87 lbs with the manual and 54 lbs with the automatic.

What remains to be seen is how these fuel-economy ratings hold up in the real world. Dissonance between EPA-ratings and real-world driving has been a problem for Ford lately.

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