Every year, industry trade journal Ward's Auto promotes powertrain excellence with its "10 Best Engines" list.

But the rise of hybrids, plug-in electric cars, and hydrogen fuel-cell vehicles has persuaded the editors to stretch the definition of "engine" somewhat.

This year, for example, three of the honorees are not standalone internal-combustion engines, but rather hybrid powertrains--with varying divisions of labor between gasoline engines and electric motors.

DON'T MISS: 2016 Chevrolet Volt First Drive: Plug-In Hybrid Home Run

That distinguished group includes the 2016 Chevrolet Volt, 2016 Hyundai Sonata Plug-In Hybrid, and 2016 Toyota Prius powertrains.

Each takes a somewhat different approach to gasoline-electric propulsion.

The second-generation Chevy Volt uses a 1.5-liter four-cylinder primarily as a generator, providing electricity to an electric motor and 18.4-kilowatt-hour lithium-ion battery pack.

2016 Hyundai Sonata Plug-In Hybrid

2016 Hyundai Sonata Plug-In Hybrid

It will clutch into the powertrain under certain circumstances to maximize efficiency once the battery is depleted. But unlike the other two winners, the Volt runs entirely on electric power for its full electric range, even under maximum acceleration. In the other two, flooring it kicks on the engine.

Among the improvements in the 2016 Volt is an increase in range, to 53 miles.

That's up from a maximum 38 miles for the first-generation Volt, and it gives the new model the second-highest electric range of any plug-in car that doesn't rely entirely on batteries--surpassed only by the BMW i3 REx, which has a 72-mile electric range.

Ward's editors praised the new Volt powertrain for its responsiveness and "gobs of torque."

ALSO SEE: 2016 Hyundai Sonata Hybrid And Plug-In Hybrid First Drive

Instead of a dedicated powertrain, the Hyundai Sonata Plug-In Hybrid uses essentially the same setup as the regular Sonata Hybrid.

It gets the 2.0-liter four-cylinder engine used in the Sonata Hybrid, but with a more powerful electric motor and larger, 9.8-kWh lithium-ion battery pack.

The Sonata Plug-In Hybrid has an EPA-rated electric range of 27 miles, but Ward's reports having 8 miles of range left after a 30-mile commute.

That--along with the gasoline engine's overall well-mannered behavior--earned the Sonata a place on the list.

2016 Toyota Prius Two Eco

2016 Toyota Prius Two Eco

Finally, the 2016 Toyota Prius is the only member of the trio that can't be plugged in (although a plug-in version will arrive within a year or so).

It uses the latest configuration of Toyota's Hybrid Synergy Drive system, with a 1.8-liter four-cylinder engine and electric motor.

Ward's was impressed by the use of new technologies--like cooled exhaust-gas recirculation--and said the new powertrain is "quieter and silkier" than the one in the last Prius.

MORE: 2016 Toyota Prius: First Drive Of 56-MPG Hybrid

The Prius also won "10 Best Engines" awards in 2001, 2004, and 2010--covering all three previous generations.

And it turns out Ward's has no qualms about including fully electric powertrains in its lists of best engines.

Lats year, it named the battery-electric BMW i3 and Hyundai Tucson Fuel Cell powertrains to the list.


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