Last year, a new generation of Ford Mustang launched, featuring the model's first four-cylinder engine since 1993.
And for that car's first model year so far, it's looking like a major contributor to the Mustang's sales success.
The 2016 Mustang is currently the best-selling muscle car, and the EcoBoost engine reportedly accounts for a significant number of those sales.
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The EcoBoost's attractiveness to younger buyers is helping the Mustang pull ahead in the sales race, reports The Detroit News.
Mustang sales were up 55 percent in the first five months of 2015, compared to the same period last year.
Between January and May, Ford sold 56,571 Mustangs according to Autodata Corp., handily beating its rivals.
2016 Ford Mustang
Both the Camaro and Challenger are only offered with V-6 and V-8 engines at the moment.
While the muscular V-8 gets most of the attention, Mustang sales may actually be dependent on the less-expensive four-cylinder engine--which more people are likely to buy.
Millennial buyers are thought to prefer the EcoBoost engine for its fuel economy, and they're now a larger share of Mustang buyers.
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Currently, 35 percent of Mustang buyers are Millennials, up from 30 percent last year.
In the important Southern California market, Mustang sales are up 117 percent, with 40 percent of cars sold going to younger buyers.
The 2.3-liter turbocharged engine is more expensive than the base V-6 but--with 310 horsepower and 320 pound-feet of torque--it's more powerful, and more fuel efficient.
It's also worth noting that the current Mustang is the newest of the three muscle-car rivals, with more modern styling that downplays the retro cues of the previous model.
2016 Ford Mustang
However, a redesigned 2016 Chevy Camaro will go on sale next year, with a 2.0-liter turbocharged four-cylinder engine.
The Mustang's EcoBoost engine is an extra-cost option, but the Camaro's four-cylinder will serve as the base engine.
Will the new Camaro dampen Mustang sales? Will consumer interest in these four-cylinder performance cars continue?
If so, there's only one thing to say.
Your move, Dodge.