"But they are not small companies anymore and we have no obligation to support them. We have to be set free now."
The value of imports from Europe was up 60 percent to $4.6 billion in the first nine months of 2014, customs data showed, against exports of $4.4 billion.
"The driving force of imported cars has been diesel engines, younger customers in their 30s and luxury brands," said Yoon Dae-sung, an official at the auto importers association, who expects further growth to be driven by mass-market, non-German cars.
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A free trade deal agreed last week with China excluded cars, to the relief of local automakers, staving off a potential influx of China-made German-branded vehicles and helping to preserve South Korea's status as one of few markets where domestic automakers hold a dominant share - for now.
In Gangnam, the epicentre of the foreign car boom, a Volkswagen store does not have enough vehicles to sell, said dealer Kim Young-chun.
"We are not taking orders for the popular Tiguan white version anymore because we have already secured about 70 to 80 orders at our store alone," he said, referring to South Korea's top-selling import, a $35,000 SUV.
As well as the support of patriotic consumers, Hyundai, its sister firm Kia Motors and others such as Ssangyong Motor Co Ltd were once protected by 50 percent import tariffs. In the early 1990s, when South Korea had a more protectionist industrial policy, some consumers shunned foreign cars for fear of being targeted for tax audits.
Trade deals have helped South Korea emerge as a source of growth for global brands, which are expanding offerings from big vehicles to smaller ones, threatening to further erode the nearly 70 percent market share held by Hyundai and Kia.
U.S. cars have not gained as much as from a similar trade pact with South Korea, the world's 11th largest car market.
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In August, BMW opened a $64 million driving center in Incheon, its first in Asia, allowing visitors to test-drive BMW and Mini cars on a 2.6-km (1.6-mile) track.
Japan's Toyota Motor, which imports its Camry sedan to South Korea from the United States, last month opened a cafe and showplace in Seoul that displays but does not sell its Lexus cars - part of efforts to raise its brand image.
In the first 10 months of 2014, foreign car sales in South Korea rose 33 percent; Hyundai sales rose 3 percent.
Hyundai is fighting back. Last month it launched its Aslan premium sedan, a rare model targeted mainly to local buyers, and recently opened a flagship store in Gangnam. Hyundai and Kia are also expanding their diesel and hybrid offerings.