It is important to know that the price of gasoline in different countries varies from time to time. The price in my answer is updated at November 2014.
The average price for 1 liter of gasoline in South Korea is 1.66 U.S. dollar.
Time of Check: 04-Aug-2014 to 10-Nov-2014.
The minimum price per liter of fuel in South Korea for that period was 1.60 U.S. dollar.
Maximum price per liter of fuel in South Korea for that period was 1.70 U.S. dollar.
For the most up-to-date price see link - See link
The average price of gasoline in the world for this period (04-Aug-2014 to 10-Nov-2014) is 1.25 U.S. dollar.
Gasoline price in South Korea is more expensive than the average price for gasoline in the world (0.41 U.S. dollar more).
Did you know that Venezuela has the world's cheapest gas, sold at government filling stations for 1 cent a liter?
Did you know that Norway has the world's most expensive gasoline, at 2.26 U.S. dollar per liter?
Car rental in South Korea
Car rental SIXT South Korea (Locations and Branches, types of rental cars etc. ) - See link
Car rental AVIS South Korea (Locations and Branches, types of rental cars etc. ) - See link
Maps and navigation apps for South Korea
Map of South Korea (Google Maps) - See link
Google Maps app for Android phones and tablets - Link
Google Maps app for iPhone and iPad - Link
Driving in South Korea using waze app for Android phones - Link
Driving in South Korea using waze app for iPhone - Link
SOURCES OF INFORMATION
IEA - International Energy Agency - link
Gasoline prices in globalpetrolprices.com - link
Gasoline and diesel usage and pricing - link
What determines the price of gasoline? and more FAQ - link