Ask the hipster waiting in line for a new iPad. Buyers and critics alike are easily seduced — sometimes too easily — by the new.

It’s no different with cars. Last year, a rare battle of the welterweights broke out. Never before, it seemed, had so many new compact models swaggered into showrooms. The Ford Focus, Honda Civic, Hyundai Elantra, Chevy Cruze and Nissan Versa were all new or completely redesigned. Which one would win the compact crown?

Yet while all eyes were focused on the main event, the Mazda 3 was in training. It now comes to market not as a stem-to-stern redesign, like those competitors, but with a transformative new engine and a pair of exceptional new transmissions.

Although the Mazda arrived relatively late, it turns out to be the life of the party. Long the sportiest, most rewarding car to drive in its class, the 3 is now the only one that effortlessly tops 40 mpg in real-world driving.

Let’s repeat that: The Mazda 3 is the best performer in the class, and it has the best mileage. That’s a pretty unbeatable combination.

Since the 1970s, of course, Mazda has worked that niche of affordable Japanese performance, enjoying hits like the Miata roadster, but never quite breaking into the big time. Fuel economy took a back seat, as with Mazda’s prodigiously thirsty, rotary-engine RX sports cars.

But with regulators circling and a 35 mpg standard brewing, there’s no longer any place to hide. Mazda says its new suite of technologies, collectively called Skyactiv, will raise its fleetwide mileage by 30 percent by 2015 with no need for an expensive hybrid system.

The 3 sedan and hatchback bear the first green fruit of this technology, including a 2-liter four-cylinder engine and equally stellar six-speed transmissions, both manual and automatic.

While the 3 doesn’t look much different, its body and cabin have received a nip and tuck. Mazda has made an attempt to fix the goblin grin of the lower grille, softening the shape of the radiator opening and slapping a larger black bar across it. But like a dental retainer, the hardware can do only so much for the Mazda’s unsightly mouth.

The interior may not be as fresh as some newer entries in the class, but it’s still awfully good. Genuine sport seats, with bolsters for both the cushion and the backrest, remind you that the 3 helped to usher in the era of premium small cars.

The old 3’s dated red instruments and displays are now an easier-to-read white. The information display proved less prone to wash out in sunlight.

Combustion-enhancing direct-fuel injection, piston cavities and an especially high 12:1 compression ratio help the Skyactiv-G engine make 155 horsepower and 148 pound-feet of torque on regular unleaded. That power-packed compression ratio soars as high as 14:1 in European models running on premium fuel. That is higher than any gasoline car engine in regular production today, including those in six-figure supercars.

With roughly 5 percent more horsepower and 10 percent more torque than before, the engine also gets 21 percent better mileage: as much as 28 mpg in town and 40 on the highway for the sedan with the automatic transmission.

The manual transmission is lighter and more compact than the one it replaces, and gets an extra, sixth gear for better mileage. The shifter “throws” — the distance the handle moves between gears — are 10 percent shorter, giving it the crispest gear changes in the class.

That a Mazda stick shift is terrific would surprise no one who’s snicked a Miata or RX-8 through its gears. But since most buyers choose an automatic, the other new transmission is the bigger story: Combining a conventional fluid torque converter, which operates only below 5 mph, with a multiplate clutch that mimics the directness of an automated manual, this smart, seamless transmission proves that innovation isn’t the province of luxury cars alone.

The competition

I should note how the Mazda amplifies the good and the bad of competitors, including the Ford Focus. Yes, in a class of cars that are able and practical but barely sporty — including the Civic, Cruze, Elantra, Nissan Sentra and Toyota Corolla — the Focus is a standout for style and performance.

Not coincidentally, that Focus shares its fine chassis with none other than the Mazda 3. The second-generation Focus, a huge advance over the original model, was sold in Europe for several years before finally migrating here last year.

Yet the Focus is saddled with a supposedly high-tech transmission — a dual-clutch automated manual — that feels clunky and overactive. In contrast, the Mazda automatic is like a slick political operative: never drawing attention, yet in charge and pulling all the right strings.

As ever, Mazda’s finely wrought steering and suspension impart a sportiness and sophistication that cannot be faked. The 3 dines on curves that will have the Hyundai, Honda or Chevy choking.

Let’s be clear: You need not be a hotfoot to enjoy the 3. To people who haven’t driven one, the best way to describe the 3 is that it drives like a junior BMW. Even the gentlest commuter can appreciate a car that feels so controlled, safe and confident.

The Mazda isn’t perfect. The 3 still lets in more wind and road noise than some rivals, especially the hushed Chevy. The Ford wins the beauty contest, especially as a hatchback.

But with Honda having largely ceded its technical and performance leadership in small cars, Mazda is among the brands stepping in to fill the void.

2012 Mazda 3

Base price: $15,995 to $25,000 and beyond

Type: Sedan and hatchback models available

Engine: For 2012, the practical hatchback has the Skyactiv-G engine as standard equipment. The 2.5 engine, which makes 168 horsepower, is still available on up-level models, although when paired with an automatic you get a mere five speeds.

Mileage: 28 mpg city, 40 mpg highway