Are gas installations in cars popular in Korea?

Yes cars running on LPG are pretty popular, especially for taxis. Since gasoline is extremely expensive in Korea, most taxis run on LPG. However, there were some strict regulations that barred people that weren’t using their car for business purposes like taxis from buying LPG cars. Basically you had to be a taxi or using your car as your business to be getting an LPG car. These regulations were alleviated in 2019, and now most people can buy an LPG car.
 
About 8% of the total cars registered in Seoul are run on LPG fuel as of 2021.