DETROIT TheStreet) -- Not to say the 2012 Fusion has been unsuccessful, but Ford ( F - Get Report) took a new approach to the 2013 version, seeking not only upgraded styling but also improved aerodynamics and fuel efficiency.

In 2012, Fusion had a good year, selling 248,067 units, making it Ford's best-selling car. But the brutally competitive midsized sector requires constant updating. Toyota (TM - Get Report) has a new Camry, GM (GM - Get Report) will soon have a new Malibu, Honda (HMC - Get Report) unveiled a new Accord at the Detroit Auto Show and Hyundai and Nissan also have popular vehicles.

So every edge counts, particularly the improvement in gas mileage that enhanced aerodynamic engineers will be able to provide.

"When we looked at aerodynamics, we attacked the entire vehicle," says Steve Parks, lead aerodynamics engineer for the Fusion. "We wanted to make sure we were squeezing all the blood we can from the turnip."

Ford says it spent an equivalent of 2 million computer hours, using parallel supercomputers, on Fusion aerodynamics. "Using techniques that have been evolving since the '70s and '80s, we used numerical equations representing airflow over a body in space," says Parks, a University of Michigan graduate who spent four years working on space shuttle aerodynamics before joining Ford in 1998.

Teams from aerodynamics, design and parts engineering worked together, focusing on three areas: the underbody shield, the grille shutters and the "top hat," or exterior body styling that is the most visible portion of the car.

The work is expected to result in a 10% reduction in aerodynamic drag, which would lead to a 2.5% fuel efficiency improvement in highway mileage. Highway mileage for the standard 2012 Fusion is 33 miles per gallon, or 36 miles per gallon for the hybrid version. Of the projected drag reduction improvement in the 2013 model, 41% would result from the improved underbody shields, 36% from styling changes and 23% from active grille shutters.

These are the five areas of improvement. The intent, in every instance, is to reduce "drag," or resistance, and to expedite the smooth flow of air around the car as it moves forward:

Underbody shields
The underbody shields minimize drag related to turbulence created by uneven surfaces on the bottom of the vehicle. "The 2012 Fusion had a nice set of shields on it, giving us some benefit, but we knew we had to go above and beyond, and we went after an excellent set of underbody shields," Park says. "They turn the underbody of the vehicle into a flat surface, so that instead of going under the vehicle and hitting components and creating drag, the air swoops past the components and exits in a nice pattern."

Most vehicles have a small number of underbody shields, but typically components such as the exhaust, rear suspension components and the fuel tank hang down, creating barriers to airflow. For instance, the 2012 Fusion had just two underbody shields; the 2013 version will have close to a dozen.

"We improved and streamlined the shields, optimizing the package, using computational fluid dynamics," Park says. "A side benefit is that when they are made of the right materials, they can diminish road noise."

Active grille shutters
A new feature on the 2013 Fusion is active grille shutters that are activated automatically at higher speeds to reduce drag.

Automobile engines generate heat. Typically, the grille enables air to flow through the radiator to help cool the engine. A disadvantage is that the airflows into the engine compartment and creates drag as it leaves through the rear of the vehicle.

"What we found is that we don't need all the capacity of the cooling system all of the time," Parks says. "At highway speed, we can close off a good percentage of the cooling path, because at that point we'd rather have the air go around or over the car and not create drag."

"It's similar to the louvered blinds on a window," he says. "These are in front of the radiator. Under conditions discerned by the engine control unit, they can close when cooling is no longer needed to improve efficiency."

Improved front and rear windshield sweep
"The way the windshield and the rear window are laid down and swept into the vehicle layout ensure air stays tight to surface and doesn't lift off the back of vehicle," Parks says. The Improved sweep ensures that the Fusion moves through the air with minimal disturbance of the airstream.

Anyone who has driven behind a truck has been exposed to the "wake," or air turbulence zone created when air gathers. This is an inefficiency reduced by better design. In the case of the 2013 Fusion, the enhanced windshield sweep also appealed to the stylists, who wanted a more swept-back look.

Improved midbody elements
The 2013 Fusion has smaller side-view mirrors, attached by a stalk or pole to the lower portion of the door panel, rather than bulkier mirrors mounted higher on the panel. The change minimizes drag and reduces wind noise. The car also has smaller quarter windows near the mirror, which enable a wider view.

Squared "rockers," or body sections beneath the doors, direct airflow around the rear tires and ensure optimal air movement along the side of the vehicle.

Additionally, the 2013 Fusion's wheel well openings are smaller to better control airflow from the front of the vehicle. Because they are smaller, less room is available for air to enter. "Typically, the air can get in there and sweep around the tires and then be spit out the side," Parks says. "We didn't want that." As in most cars, spoilers, or small flaps placed in front of the tires, guide air around the tires.

Improved rear design elements
Rear quarter panels have been redesigned and rear corners have been sharpened "so that the wake is as stable and small as possible, reducing turbulence," Parks says.

"We looked at the way the air wants to come back together at the rear of the vehicle," he says. "After it has been pushed aside, it wants to come back together as smoothly as possible, and we have tapered the car to ensure that it can do this with as little disturbance as possible."

Also, a rear underbody shield, behind the muffler, allows for smoother reassembly of the airflow stream behind the vehicle.

Finally, the new Fusion has a raised edge at the rear of trunk, which ensures that the air remains close to the vehicle for as long as possible, minimizing the size of the wake.

>To contact the writer of this article, click here: Ted Reed

>To follow the writer on Twitter, go to

>To contact the writer of this article, click here: Ted Reed