INFINITI redefines its Q50 lineup for 2018 with a new trim lineup and a choice of four solid power plants. The Q50 is the company’s best-selling model, accounting for one-third of all sales.

It’s pretty easy to see why. I had a blast tooling around town in this little red number. It’s fast, it’s nimble, it’s comfortable and it’s sexy.

The 2018 Q50 will be available in Pure, Luxe, Sport and Red Sport 400 trim levels, each with more of their own look and character.

The Pure and Luxe get a standard 2.0-liter turbocharged four-cylinder engine that delivers 208 horsepower and 258 lb.-ft. of torque. The Lux and Sport trims have an available 3.0-liter twin-turbo V6 that kicks out 300 horsepower and 295 lb.-ft. of torque. All of the above engines are hooked to a 7-speed automatic transmission.

The top-end Red Sport 400 gets the same V6, but it is tuned to kick out 400 horsepower and 350 lb.-ft. of torque. That was the engine in my rear-drive test Q50 for the week, and boy did it deliver an exhilarating driving experience. The Q50 felt right at home on Interstate 12, on River Road and on curving Feliciana roadways.

The Red Sport 400 comes with 19-inch wheels shod with run-flat summer tires, which not only enhance the look, but improve handling and traction.

Inside the cabin of the Q50 you’ll find excellent craftsmanship, quilted leather seats and aluminum trim. Soft touch materials are in all the right places, and red accent stitching crosses the dash.

Dual screens top the center stack, with the navigation screen on top (8 inches) and the touch controls on the lower screen (7 inches). The console has a rotary controller and a switch to adjust camera views.

There’s also a toggle switch to adjust the vehicle’s drive mode: personal, sport, sport-plus, standard, ECO and snow.

Connectivity is via INFINITI’S InTouch system, which allows personalization for multiple drivers. SiriusXM Travel Link is now complimentary for four years instead of just six months, with a SiriusXM satellite radio subscription.

The sound system is Bose and has 16 available speakers. Other features include dual-zone air, Bluetooth, a rearview monitor, automatic headlights, a tilt and telescoping steering wheel, rai-sensing wipers, a heated steering wheel and remote start.

Headroom inside the Q50 is decent at 39.5 inches in the front seat. In the rear seat, the hair on top of my 6-foot-1 frame brushed the headliner. Legroom in back (35.1 inches) is made larger by the concave front seatbacks. Trunk room is 9.4 cubic feet.

Out on the road, the Q50 does not disappoint. It’s a comfortable daily driver, but when you mat the accelerator, the car responds immediately and aggressively, especially in sport and sport-plus driving modes. It’s a difficult balancing act, and the Q50 pulls it off nicely.

Our test Q50 Red Sport 400 was EPA rated at 26 miles per gallon on the highway and 20 mpg in the city. A gas/electric hybrid model is offered, with EPA ratings of up to 30 mpg on the highway and 26 mpg in the city.

When it comes to safety, the Q50 has all the latest sophisticated equipment that aims to prevent accidents in the first place. A full complement of airbags including side curtains, blind spot warning, rear cross traffic alert, backup collision intervention, predictive forward collision warning and forward emergency braking are standard.

Neither the government nor the insurance industry has yet completed crash tests on the 2018 Q50.

2018 INFINITI Q50 Red Sport 400

Engine:

3.0-liter twin-turbo V6

Horsepower/Torque:

400/350 lb.-ft.

Transmission:

7-speed automatic

Price:

$51,000 (plus options & freight)

EPA mileage rating:

20 mpg city/26 mpg highway/ 22 mpg combined

Estimated highway range:

463 miles