Hyundai Motor Group is moving to minimize the impact of the gas mileage overstatement after admitting last week to “errors” regarding some 900,000 vehicles it sold in the U.S. between 2010 and 2012.

The American unit of the Korean auto giant issued a public apology in major U.S. newspapers, while the group chairman Chung Mong-koo summoned executives for an urgent meeting in Seoul on Monday.

On Friday, the carmaker apologized to customers after the U.S. Environmental Protection Agency found errors in mileage estimates of 13 Hyundai and Kia models.

“With the appropriate corrections in place, the 2012 Hyundai/Kia fuel economy level is reduced by an average of 3 percent,” the full-page ad said, citing “procedural errors” in mileage testing.

Together with replacing mileage stickers on the windows of the affected cars, the company pledged to start a reimbursement program immediately, which could be worth some 86 billion won, or about $80 million.

Industry watchers here predict some negative impact on Hyundai and Kia’s brand image and business would be unavoidable, with some raising the possibility that the current mileage fallout could be followed by a large-scale group lawsuit.

“The mileage overstatement was found in almost all the Hyundai and Kia models sold in the U.S. Their brand image is likely to be affected negatively,” said Nam Kyung-moon, an analyst at KTB Investment and Securities.

“Hyundai has promoted its vehicles based on their high fuel economy. The errors would influence consumers who are considering car purchase,” said Choi Joong-hyuk, a researcher at Shinhan Investment.

Critics and Hyundai officials, however, say the latest mileage inflation cannot be compared with the massive recall of Toyota cars in 2009, whose brake issue was directly linked to the safety of drivers.

“Toyota lost consumer trust at the time as it attempted to avoid taking responsibility and responded too slowly. Compared to that, Hyundai is moving fast,” said Seo Sung-moon, an analyst at Korea Investment and Securities.

Kim Pil-soo, professor of automotive studies at Daelim University, also pointed out that the best policy for now is a speedy response.

“Hyundai should minimize the impact in its sales momentum in the U.S. market. The company also needs to get ready against Japanese rivals that would step up their offensive,” he said.

Amid mixed outlook among industry watchers, shares of Hyundai Motor and Kia Motors on Monday suffered an almost 7 percent decline.

Hyundai officials said the mileage tests conducted at the company’s Korean tech center seemed to have failed to sufficiently take into consideration the real-world conditions in the U.S. But they denied that there were similar errors in the cars sold in the Korean market.

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