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Chevrolet began production of the original small-block V8 engine for the 1955 model year and effectively kicked off what would become a more-than-60-year love affair among Americans. Since its initial debut, the small-block V8 has remained in constant production, making it the longest mass-produced engine internationally. Despite constant innovation and improvements, many automakers are pulling away from the American powerhouse in the face of federal fuel efficiency regulations.

The federal government formed an agreement with major automakers to raise the average industry-wide fuel efficiency standard to 54.5 miles per gallon by 2025. With just eight years to the deadline, automakers have no choice but to look to alternative energy and smaller, more efficient engines and the results are rather depressing.

The Ford F-150, otherwise known as the bestselling vehicle of all time, has recently seen the V8 engine take a backseat to the more efficient, and powerful, EcoBoost V6. General Motors is cutting the V8-powered Chevrolet SS from the lineup. Ram offers an EcoDiesel V6 engine that earns just shy of 30 miles per gallon. Even the returning Ford GT supercar comes to the road with a 3.5-liter EcoBoost V6 engine, albeit with an output of 647 horsepower.

Classic American muscle, like the Chevrolet Camaro and Ford Mustang, can't escape the grip of fuel efficiency standards either. Both models have seen the addition of new turbocharged four-cylinder engines within the last few years. Performance-driven V8 engines are still available for the time being. Notably, Ford plans to drop the V6 engine from the Mustang's range for the 2018 model year.

Even the most efficient automakers, some of which lack a V8 engine throughout their lineup, are feeling the pressure. Mazda leads the industry when it comes to fuel economy, earning an average of 30.7 miles per gallon. Nissan comes in second, earning an average of 29.5 miles per gallon. Honda rounds out the top three, rated at 28.7 miles per gallon.

The bottom of the fuel-efficiency barrel brings those that make due with larger engines, namely well-known American brands. Despite new engine offerings throughout the lineup, Fiat Chrysler, which also includes Dodge, Jeep, and Ram, earns an average of just 22.2 miles per gallon across the board. Ford comes in second worst, earning 23.4 miles per gallon. General Motors saw the return of the Colorado and Canyon midsize pickups, resulting in an average rating of 24 miles per gallon.

Automakers are making stringent cuts in order to comply with federal regulations, but progress is slow. Mazda has implemented GDI technology throughout its lineup. BMW, Volkswagen, Mercedes-Benz, and Ford have turned to turbocharging. Honda, General Motors, and Fiat Chrysler have begun to add cylinder deactivation to more vehicles across their lineups.

Others are teaming up to develop more fuel efficient technologies. Ford and General Motors formed a partnership to develop two new transmissions. The nine-speed automatic transmission currently comes available in passenger vehicles. A 10-speed automatic transmission is available in trucks and muscle cars, like the Ford F-150 and Chevrolet Camaro.

Despite fuel efficiency regulations, American consumers aren't seeing eye-to-eye with the federal government. Sales of larger, more spacious vehicles, such as crossovers and SUVs, have seen a dramatic increase in recent years. With gasoline prices well below $3 a gallon in most states, hybrid and electric vehicles have become less popular, putting automakers at a crossroads with federal regulators.

The Alliance of Automobile Manufacturers, which represents General Motors, Fiat Chrysler, and Ford, among others, wrote a letter to the new head of the Environmental Protection Agency (EPA). The letter urged the EPA to reverse the 2025 fuel efficiency standards, citing the difficulty and cost to meet such a high target.

American automakers aren't the only ones taking a stand though. The Association of Global Automakers wrote a second letter on behalf of a dozen foreign automakers requesting the same thing. Still, the United States isn't the only country that holds high efficiency standards. China, which recently became the world's largest automotive market, is on board as well.

Unless automakers find a way to dramatically increase fuel economy over the next eight years, the number of vehicles with V8 engines will likely continue to diminish. As a result, this could very well be the beginning of the end of America's love affair with the V8 engine.

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