Courtesy Ford Motor Co. via The New York TimesFord’s pony car has been at the core of Americans’ automotive enthusiasm for half a century, and the new Mustang hearkens back to older styling cues while adopting more muscular proportions.

SANTA BARBARA, Calif. — There are Mustangs stuck in my mind. There’s the red ’68 California Special coupe I saw parked at a neighbor’s house every day as I walked by to La Cumbre Junior High School. It was too beautiful to touch.

There was the blue ’74 Mustang II fastback that my friend Gayle Van Leer drove when she wasn’t atop actual thoroughbreds, training them to race. She was so self-confident and capable, she made that miserable car seem exciting.

And there was the ’94 GT that I piloted on the empty freeways on Christmas morning 1994 from Santa Barbara to my sister’s house in San Diego, at speeds of which I am both proud and ashamed.

Those Mustangs, and at least a dozen more, will be with me the rest of my life.

Ford’s pony car has been at the core of Americans’ automotive enthusiasm for half a century. Of the cars that people dream of owning, it’s one of the few they may actually afford. It’s not pretentious like a Cadillac or Lincoln, nowhere near as impractical as a Corvette and not vulgar like a monster truck or a lowrider. And it sure isn’t German, British, Italian, Korean or Japanese.

But the Mustang is a car that has no practical reason to exist: It is about exuberance, freedom and fun. It is a particularly American vehicle engineered for the American pursuit of happiness.

So when a new generation of Mustang arrives, the American automotive culture reorients itself. And this new 2015 Mustang is very new.

The 2014 Mustang was the last rear-drive car sold in America that still had a solid rear axle — just like the Model T. The most significant mechanical change for the 2015 model is the adoption of an independent rear suspension across the Mustang range for the first time.

The independent rear suspension is standard on every new Mustang from the base coupe, powered by a 300-horsepower 3.7-liter V-6, to the new 310-horse EcoBoost version with a turbocharged 2.3-liter 4-cylinder engine, and on to the GT with a mighty 5-liter V-8 rated at 435 horsepower. There’s also a Shelby GT350 model coming in 2015, powered by a 5.2-liter V-8 that will make more than 500 horsepower.

I drove two preproduction fastback coupes: the EcoBoost with a 6-speed automatic transmission, and a GT with the 6-speed manual. The base V-6 engine essentially carries over from the 2014 model, and it’s likely to still be the best seller.

While Ford’s interior materials have improved, they still convey a sense of unpretentiousness — or chintz, take your pick. The seat leather is overprocessed, and the plastics are rigid and rough-grained. Toyota and Audi have nothing to fear in here.

The eight airbags in the new Mustang, including a knee cushion embedded in the glove box door, double the number of airbags used before.

It’s the Mustang’s structure that has vastly improved. Every body panel fits more precisely than before, and the doors shut with impressive thuds. The car is not roomy inside, and the back seat is still nigh on useless, but the driving position and visibility have both been improved.

Press the Start button on the EcoBoost 4 and, well, nothing. There’s no distinct exhaust note, and the engine idles quietly. Ford has incorporated a twin-scroll turbocharger and direct injection into this engine, but hasn’t installed much of a personality. With a 0 to 60 time of 5.2 seconds, according to Car and Driver, it’s a relatively quick car. It just doesn’t feel as if it’s doing much when it’s hooked to the automatic transmission.

Arguing in favor of the EcoBoost engine are solid EPA fuel-economy ratings: 21 mpg in the city and 32 mpg on the highway. The base V-6’s numbers of 19 city and 28 highway are behind that, but not so far back that the $1,570 premium Ford charges for the turbo EcoBoost makes strict economic sense.

In contrast, the 5-liter V-8 in the GT has an utterly theatrical character. It growls at idle and then rockets like an Allman Brothers guitar harmony as it hits its stride. Ripping through the manual transmission’s gears is easy, and the chassis comes to life as the V-8’s 400 pound-feet of peak torque surges through it.

The GT works as a solid piece with the optional Performance Package’s 255/40HR19 front Pirelli tires biting in to turn the car and the tail’s 275/40HR19 tires following in a neutral, easy arc as it corners. The suspension is adjustable, but it feels tenacious even when tuned to its softest setting. When set at its stiffest, the ride is always controlled and relatively comfortable.

Every Mustang GT gets an electronic launch control program and, more playfully, a line lock system that will lock the front brakes so the driver can spin the rear tires in that most adolescent of automotive displays, a tire-frying burnout.

The GT is a seriously quick and fast car: Car and Driver measuring a 0 to 60 mph time of 4.5 seconds and a quarter-mile performance of 13 seconds at 113 mph. A governor restricts the car to a top speed of 164 mph.

There’s still a lot of Mustang in how this new model feels — nervy and eager — but also the confidence of a big German coupe. And it’s as satisfying to drive slowly as quickly.

While a base Mustang V6 coupe starts at $23,600, getting into a GT will take at least $32,100. Most Mustangs will leave the dealer’s corral with a sticker price of at least $30,000, and GTs, after options, will generally run past $40,000. Convertible models are $5,500 more expensive.

Enthusiasm defines all the pursuits of happiness in American culture. The newspaper in your hands (or on your screen) is built around them — religion, arts, sports, business, politics, fashion, books, cooking — and the enthusiastic response to the new Mustang shows how vital the love of cars still is. Every car is a big financial commitment, and a car like the Mustang makes that commitment an easy one.

By rational standards, the overpowered, overstyled and space-inefficient Mustang makes no sense. It doesn’t have to. It’s too American for that.