By Ann M. Mob

Here’s an intriguing fact: The Infiniti M luxury sedan that’s listed in the Guinness Book of World Records for its acceleration prowess is the same M that has the best fuel economy rating of the lineup.

It’s because the Guinness record holder is the new-for-2012 M35 Hybrid, which pairs a gasoline V-6 to an electric motor and lithium ion battery pack and manages the power through a seven-speed automatic transmission. There’s no continuously variable transmission (CVT) here.

The M35h’s combination powerplant can move the more than 4,100-pound, four-door car from standstill to 60 miles per hour in 6.1 seconds while pushing passengers’ bodies firmly into the seatbacks.

This figure, provided by Infiniti, is akin to the performance of a new Chevrolet Camaro with V-6.

Yet, the M35h’s federal government fuel economy rating of 27 miles per gallon in city driving and 32 mpg on the highway is the highest of all the M models. For example, the base 2012 M37 with V-6 and no electric assist is rated at 18/26 mpg.

But even with today’s gasoline prices that top $3.90 a gallon, it would take M35 Hybrid drivers a while to recoup via gasoline savings the $6,000 premium that the hybrid model costs over a non-hybrid M37.

And there are other hybrids, even luxury hybrids, that have lower starting prices than the M35h’s $54,595. They also have higher fuel economy, though not the record-breaking acceleration.

For instance, the 2012 Lincoln MKZ Hybrid mid-size sedan, which has a starting retail price of $35,630 is rated by the federal government at 41/36 mpg. The MKZ is a gasoline-electric hybrid with a four-cylinder engine mated to an electric motor and so doesn’t have the power of the M.

The 2012 Lexus HS is a compact, luxury, hybrid sedan with a retail starting price of $37,905 and fuel efficiency rating of 35/34 mpg. The HS is powered by a four-cylinder engine and an electric motor.

The M35h is the first hybrid for Infiniti, and the brand didn’t stray from what it’s known for — performance and luxury.

But the test M35h seemed as much a showcase for technology as it did for showing that a hybrid can be fast and exhilarating.

Much of the M35h’s technology, including the navigation system with voice recognition and on-board Zagat restaurant ratings, was optional and helped push the final sticker price to more than $67,000.

But it made an indelible impression of a car filled with so many electronic bits that it just might drive itself one day.

Note: To keep from being overwhelmed, it’s best for a driver new to an option-packed M35h to take a deep breath and learn the different driver aides one by one. Example: The optional lane departure warning gives one kind of audible warning if the car starts to drift from its lane.

Another audible warning, standard on the car, arises when the M35h is in all-electric mode, because otherwise it’s a silent vehicle that pedestrians might not notice. Infiniti was the first to put this pedestrian-alerting system on a car. Federal government officials have been debating whether to require audible alerts on all cars that have an electric mode.

The M hybrid system eschews a torque converter and instead uses a wet clutch and a dry clutch to manage the power from the 302-horsepower, 3.5-liter, double overhead cam V-6 and the 67-horsepower electric motor.

Drivers don’t see or operate the clutches. The clutches work automatically to decouple the engine from the transmission at stops, so fuel is saved at stoplights, and allow the M35h to travel up to 62 mph on electric power alone.

It also can stay in electric mode for 1.2 miles, which is longer than many other hybrids.

The M35h judiciously monitors battery reserves and goes right to gasoline-power-only when necessary.

The test M35h required careful throttle control at startup, because the car was eager to zoom forcefully forward in electric mode from a stop.

This affected the test drive and brought an average of just 27.6 mpg in travel that was 70 percent in city traffic.

An M35h hallmark is the lack of a CVT. Other hybrids have had CVTs because these transmissions can maximize fuel economy. But they are not the top choice for acceleration.

Unfortunately, when the V-6 power would join in, there often was noticeable roughness in the test car. It was not the seamless transition that some hybrids deliver.

As is typical in hybrids, the brakes on the M35h had an artificial feel and didn’t operate with a pure linear response as the brake pedal was pressed. This is due to the car’s regenerative braking that captures energy and recharges the battery pack as the car is braking.

The M35h is a handsome sedan with stylish wheels and regular, not low-rolling resistance, tires. The tester had optional, large, 18-inch tires, which conveyed a good amount of road noise.

The M35h had a substantial, solid feel, and while the battery pack adds weight to the car vs. the M37, the hybrid feels well-balanced on twisty mountain roads. The only exterior clue that the car is a hybrid is the word “hybrid” on two fenders and the little “h” next to M35 on the trunk lid.

The interior has the luxurious atmosphere of all M cars, and control buttons on the dashboard are large, with good tactile feedback. Fit and finish on the tester was excellent.

Trunk space measures 11.3 cubic feet, down from the 14.9 cubic feet of a non-hybrid M37 because the battery pack takes up some trunk space.

2012 Infiniti M35h

This undated product illustration made available by Nissan shows the 2012 Infiniti M35h. The M35h’s combination powerplant can move the more than 4,100-pound, four-door car from standstill to 60 miles per hour in 6.1 seconds while pushing passengers’ bodies firmly into the seatbacks. (AP Photo/Nissan)

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