In Detroit, fuel economy rules

NEW YORK (CNNMoney) -- Every auto show, these days, is "all about plug-in cars and hybrids," they say. Everyone's gawking at the cherry on top while few notice how different the ice cream underneath is.

At the 2012 North American International Auto Show in Detroit, you can see the auto industry changing -- deeply, quickly and probably forever. The reasons are stricter fuel economy regulations and changing attitudes toward environmental responsibility.

Yes, those are things car companies talk about when showing off cars such as the new Ford Fusion Energi plug-in hybrid or the Acura NSX hybrid performance car concept.

But fuel economy and the environment are, just as much or maybe even more, the reasons that cars such as the Dodge Dart are equipped with fuel-efficient 4-cylinder engines, or why General Motors (GM, Fortune 500) unveiled the very small Buick Encore compact SUV.

They're also why there was one notable omission from this year's Detroit show. Not a single truck or large SUV was unveiled at any of the show stands this year. There have been auto shows in recent memory at which it seemed there were nothing but massive trucks rolling out under every drape.

Cool cars from the Detroit Auto Show

There were SUVs, of course -- there always will be -- such as the Buick Encore.

There was also the new Nissan Pathfinder, but even that roomy, 3-row SUV proves the point that fuel economy has become the big bogie. The Pathfinder you see on the roads today is a truck-based vehicle built to withstand real off-road use. The new one rides on car-like engineering, which will allow it to be lighter and less thirsty.

Engines themselves are getting smaller, too. Even the venerable Bentley is downsizing. The British ultra-luxury automaker unveiled the Continental GT V8 at the show.

Under the hood of this car is a relatively modest twin-turbocharged 4.0-liter V8 which, Bentley estimates, will quaff 40% less premium than the 6.0-liter V12 in the less stingy version of the car. Even with the V8, performance will still be "exhilarating," Bentley promises.

In more pedestrian cars, the "bigger engine" option is pretty much out. Today, the Ford Fusion is available with a V6 engine. The new one will not be. Only various 4-cylinder engines will be offered. The Dodge Dart, as well, will be available only with 4-cylinder engines.

Even performance is being subtly redefined. It used to be that performance was measured in one, single, easily stated number: horsepower. In auto shows past, carmakers would compete to see who could unveil the car with most eye-popping horsepower number.

And that's not entirely over. Shelby American Inc. was on hand with its display of modified Ford (F, Fortune 500) Mustangs with horsepower outputs stretching all the way to a gut-crunching 800.

The "new performance" could be found at the Subaru and Toyota (TM) stands, where the identical Subaru BRZ and Scion FRS were on display. These cars put out a relatively slight 200 horsepower out of 2.0-liter flat-four engines. That's an impressive figure, given the size of the engine and the fact that it doesn't have a power-boosting turbocharger or supercharger.

But these cars aren't about zero-to-60 times, Scion and Subaru representatives say. They're about driving fun. Engineers put the engine as low as possible in the car to create the lowest possible center of gravity, the idea being to optimize cornering while still going quick enough to produce a healthy grin.

This new trend in less showy fuel economy was perhaps best exhibited in the show's opening moment. A jury of automotive journalists awarded the North American Car and Truck of the Year Awards to the Hyundai Elantra and the Land Rover Range Rover Evoque.

The Elantra, a compact car, gets 40 miles a gallon without sacrificing driving fun. The Range Rover Evoque uses a turbocharged 4-cylinder engine to provide enjoyable driving performance while still getting an impressive -- in this context -- 22 miles per gallon in combined city and highway driving.

Of course, there are still those plug-in cars. But with standard, run-of-the-mill gasoline-powered cars pushing the fuel economy bar ever higher, they seem likely to remain car show sideshows for a few years longer.