Now in its 17th year, the Ward's 10 Best Engines competition breaks new ground by adding an entirely new category of propulsion system: electric vehicles.

Three hybrid-electric vehicles have made the list in the past, including the Toyota Prius. Some readers questioned our sanity for recognizing vehicles designed specifically to bypass the gasoline-powered engine to save fuel.

This latest decision to include the Chevrolet Volt and Nissan Leaf in our testing will be even harder for some folks to swallow. The Leaf doesn't have an engine — just batteries and an electric motor.

The Volt has an engine, but it doesn't run unless the electrical range has been depleted, somewhere between 25 and 50 miles (40-80 km). Unlike current HEVs, the Volt always is propelled with electric power delivered by a traction motor.

Before readers begin composing their “how could you?” emails in protest, let us provide some justification.

True, the gas engine takes a back seat in the Leaf and Volt. Semantics aside, these two vehicles have propulsion systems — pretty good ones at that.

If these vehicles can keep up with traffic on the highway without consuming a drop of fossil fuel, then we would be shirking our duties by leaving EVs out of the mix.

Don't forget that honoring the application of new technology has been a hallmark of Ward's 10 Best Engines from the beginning.

Besides, many of the powertrain teams we recognize at our awards banquet — Jan. 12 during Detroit's North American International Auto Show — have been redeployed to help their companies meet strict fuel-efficiency targets that will become more challenging in coming years. If EVs are good enough for them, they're good enough for us.

This year's competition follows the proven template we've used since 1995: In August and September, Ward's editors identify new powertrains to include in the competition, then spend October and November testing them.

Editors fill out scoresheets for every vehicle driven. Points are awarded for overall power; noise, vibration and harshness; the engine's technical attributes; and its relevance among direct rivals.

Winners will be named in mid- December. The inclusion of electric vehicles should not overshadow the fact this year's field represents the most diverse, power-dense group of new engines ever evaluated by Ward's.

We have muscle-car V-8s, two diesels, four conventional hybrids and a raft of peppy 4-cyl. engines. In all, 38 engines are in the running — more than any previous year.

Clearly, the arrival of the modern EV requires the biggest adjustment for Ward's 10 Best Engines judges — the same as it is for all American consumers. Suddenly, finding a gas station is less important than finding a plug, especially with the Leaf.

For future EV evaluations, a 240V charger on loan from Delphi Corp. and ClipperCreek Inc. soon will be installed in the Ward's parking deck in Southfield, MI, and will be compatible with multiple EVs as they come to market.

Going forward, any vehicle that reinforces the notion of enjoyable driving while meeting mobility needs with the greatest efficiency will be eligible for Ward's 10 Best Engines consideration.

2011 Ward's 10 Best Engines Nominees

Returning winners and applications tested
2.0L turbo I-4 Audi A4 Avant
3.0L supercharged V-6 Audi S4
3.0L I-6 turbodiesel BMW 335d
3.5L EcoBoost V-6 Ford Taurus SHO
2.5L I-4 HEV Ford Fusion Hybrid
2.4L Ecotec I-4 Chevrolet Equinox
4.6L Tau V-8 Hyundai Genesis
2.5L turbo H-4 Subaru Legacy GT
1.8L I-4 HEV Toyota Prius
2.0L I-4 turbodiesel VW Jetta TDI
New entries and applications tested
3.0L turbo I-6 BMW 335i
3.0L twin-turbo I-6 BMW 335is coupe
3.6L Pentastar V-6 Dodge Avenger
6.4L Hemi V-8 Dodge Challenger
1.6L I-4 Ford Fiesta
3.7L V-6 Ford Mustang
5.0L V-8 Ford Mustang GT
5.4L supercharged V-8 Ford Shelby GT500
6.2L V-8 Ford SVT Raptor
1.4L turbo I-4 Chevrolet Cruze
1.4L I-4 EREV Chevrolet Volt
1.8L I-4 Chevrolet Cruze
2.0L turbo I-4 Buick Regal
6.2L LS3 V-8 Corvette Grand Sport
1.5L I-4 HEV Honda CR-Z
2.4L I-4 Hyundai Sonata GLS
2.4L I-4 HEV Hyundai Sonata Hybrid
2.0L turbo I-4 Hyundai Sonata 2.0T
5.0L Tau V-8 Hyundai Genesis
2.5L VQ V-6 Infiniti G25
3.5L V-6 Kia Sorento SX
1.5L I-4 Mazda2
1.6L turbo I-4 Mini Cooper S
80 kW electric motor Nissan Leaf
1.6L turbo I-4 Nissan Juke
2.5L H-4 Subaru Forester
4.0L V-6 Toyota 4Runner
3.0L turbo I-6 Volvo S60