It took a while, but for 2012, Infiniti has finally introduced its first ever gasoline-electric hybrid vehicle. By choosing its top-of-the-line M class of vehicles, Infinity makes its hybrid one of the most economical luxury sedans without compromising power and performance.

The Infiniti M class, which is also offered in the M37 gasoline V-6 and M56 V-8 before hybridization, is a terrific car — a driver’s dream, if you will. We reviewed the M37 last May and found it nearly flawless. The M hybrid version is virtually identical to the non-hybrid M vehicles inside and out, however, it is not available with all-wheel drive or Infiniti’s Sport Package, which improves handling with an upgraded suspension.

Nissan, Infiniti’s parent company, previously offered only one hybrid, the Altima, but discontinued it last year because of extremely low sales numbers. The Altima bought the hybrid system used in the Camry from Toyota.

The hybrid system that powers the new M is the first developed by Nissan, who say they will no longer rely on Toyota or other manufacturers for their hybrid systems. Infiniti calls it the Direct Response Hybrid System, and it can propel the M hybrid up to speeds of 62 mph on its 50-kW electric motor for up to 1.2 miles before the gasoline burning 3.5-liter V-6 kicks in. The electric motor is rated at 67 horsepower and the gasoline engine at 302 horsepower for a combined net output of 360 horsepower. On the highway, the M gets an estimated 32 mpg, while the city is rated at 27 mpg. Our hybrid test car got about 25 mpg overall during our weeklong testing.

Note that there is no plug-in capability with this new generation hybrid. Battery power comes from a lithium-ion pack positioned between the rear seats and the trunk. As a result, the trunk is considerably smaller than in the gasoline-powered M, and there isn’t a pass-through. Infiniti says it will hold four sets of golf clubs, but we tried to fit a larger piece of luggage back there without success.

One of the major benefits to driving the M hybrid is that it doesn’t compromise performance. With a 0-60 time of 5.0 seconds and a standing quarter-mile covered in just 13.9 seconds, it is the quickest hybrid ever.

But all this performance isn’t cheap. The Hybrid has a base price $6,000 more than the standard M37 gasoline version, and both vehicles are equipped about the same.

Our test vehicle had a base price of $57,300 and came with a $3,800 optional Deluxe Touring Package that adds Japanese White Ash wood trim, semi-aniline leather appointed seats, suede-like headliner, and a power rear sunshade. It also included a $3,350 Premium Package with hard drive navigation, 8-inch color touch screen display and voice recognition, climate-controlled heated and cooled front seats, a heated steering wheel, and a Bose 5.1 channel, 16-speaker premium audio system. Add optional 18-inch wheels ($650), a trunk mat ($200), and illuminated door sills ($360), and the total price including the $895 destination charge brought the MSRP to $62,955.

Even at that price, the M Hybrid was plagued with the same noticeable and annoying “hybrid shake and shudder” when the engine switches out of electric mode and the gasoline engine fires up and restarts. The vehicle is dead silent while stopped at a light and accelerates with a light-as-a-feather touch on the gas pedal, allowing you to operate on electric power only. Press a bit firmer, and the gasoline engine restarts.

Even at uneven, commuter-type highway speeds, the gas engine will shut off almost immediately when you back off the accelerator, causing the vehicle to revert to EV mode while coasting. Ease back on the pedal and the M Hybrid will stay in electric mode for at least a short distance. Other than the shudder, the constant toggling between the electric and gasoline engine is a seamless operation.

Also, a knob on the console allows a choice of driving modes including Eco, Snow, Sport, or Standard. We drove almost exclusively in Standard mode since Eco mode so completely detuned the throttle response, taking all the pleasure out of driving a vehicle that could barely get out of its own way.

Snow reduces the amount of torque to the rear wheels and is meant to do exactly as indicated — prevent the car from losing traction on icy and slippery roads. Sport mode keeps the engine rpm speed above 3,000 for immediate performance power when desired, however, it will still switch to electric-only drive mode when conditions call for it.

Sport mode also affects the transmission, which explains why there is no separate sport setting on the shifter. With seven gears, the automatic transmission helps the car's fuel economy mission. A manual mode lets the driver shift through the gears sequentially, and allows more aggressive driving than in Sport mode.

For now the mid-sized luxury sedan class of vehicles isn’t exactly flush with options, leaving the M Hybrid as the lone purely hybrid choice. A newly redesigned Lexus GS 450h should hit the market soon and a hybrid version of the Audi A6 is also on the horizon.

Other mid-sized luxury sedans like the Mercedes-Benz E350 BlueTEC diesel, BMW 528i, or Audi A6 2.0T all will deliver more than 30 mpg but not the performance power you’ll experience with the Infiniti M Hybrid.