After years of hand-wringing over fuel economy, Americans are once again buying flashy, powerful muscle cars — defying the skeptics and sending automakers scrambling to meet demand for the horsepower-heavy machines, NBC News reported. Only a few years ago, automotive critics expected V-8 engines to cede to hybrids and battery-powered cars. But muscle car sales have risen more than 35 percent over the last nine years, and now there are more on the road than there have been in decades. Dodge's new "Hellcat" models of the Challenger and Charger are the most powerful muscle cars to ever roll off a Detroit assembly line, and they're already sold out for the rest of the 2015 model year.
