Losing vehicle weight through the use of aluminum is currently all the rage among global carmakers.

Jaguar rolled out the all-aluminum XJ and XF sedans, while Mercedes-Benz’s new C-Class used aluminum for almost half the body structure.

The use of aluminum, a lighter alternative to steel, means reduced weight and better fuel efficiency.

The C-Class, for instance, is some 100 kilograms lighter than before, with its fuel ratings improving by 20 percent.

With carmakers pouring resources into reducing vehicle weight, Korea’s Hyundai Motor, however, appears to be bucking the trend.

Since November last year, Hyundai and its affiliate Kia Motors have launched five new models, including the Soul, Genesis, Sonata, Carnival and Sorento, all top-selling models in their segments. 

All the cars have gained from 27 to 100 kilograms in weight and only two models, the Sonata and Carnival, show better fuel ratings. However, the improvement for the Sonata was a tiny 0.2 kilometers per liter.

“The Sonata has gained some 50 kilograms due to its larger size and more safety features,” said Hyundai’s marketing director, Kim Sang-dae. “We are also remorseful about the fuel economy.”

Hyundai, which owns Hyundai Steel, the nation’s second-largest steelmaker, has expanded its use of high-strength steel in manufacturing its new cars as part of enhanced safety efforts in recent years. 

The efforts have paid off on the safety side. In separate accident tests by the U.S. Insurance Institute for Highway Safety, the Sonata and Genesis received their best ratings ever, respectively.

But industry watchers point out that while safety is a crucial issue, better fuel efficiency is what consumers want.

“Some luxury carmakers are now turning to even lighter and pricier materials like carbon fiber for better fuel economy and driving agility,” said an automotive expert on condition of anonymity.

“Hyundai may have thus far built its reputation on its safety and cheaper pricing. But now is the time for the world’s fifth-largest carmaker to offer something different or follow the global trend at least.”

The lower-than-expected fuel ratings are hurting car sales.

Considering that the previous Sonata sold some 16,000 vehicles per month in the first year of its launch back in 2009, monthly sales of the all-new Sonata, which was launched in March, fell to some 6,000 units in August.

The fiercer competition, with cheaper, more fuel-efficient foreign-brand models joining the market, is also cited as one of the factors that is dampening the car sales of Hyundai and Kia.

In the meantime, the two companies are also gradually adopting lighter materials.

Hyundai’s high-end sedans like the Genesis and Equus have a hood and fenders made of aluminum, while the panoramic sunroof frame of the Kia Sorento uses carbon fiber ― the first of its kind in a Korea-made car.

By Lee Ji-yoon (jylee@heraldcorp.com)