* First Mexican crude purchase since 1990 -customs data
* GS Caltex looks to procure cheap crude as prices remain weak
* Similar purchases likely if cheap spot available -spokesman
* Another Mexican crude on the way for another Asian refiner -Reuters data (Adds Pemex shipping 5 million barrels to South Korea recently)
By Meeyoung Cho
SEOUL, March 9 (Reuters) - South Korea's GS Caltex Corp has bought Mexican crude for the first time in 25 years to take advantage of low prices to make cheap spot purchases, a spokesman said on Monday.
GS Caltex, the country's second-biggest refiner, bought 1 million barrels of crude from Mexican state oil company Pemex, which arrived late on Sunday, he said.
Separately, Pemex said between January and April 2015, it will have exported about 5 million barrels of crude to South Korea, with about 80 percent of it going to Hyundai Oilbank Co Ltd and the rest to GS Caltex.
The crude is being sent in 1 million-barrel shipments, 80 percent of it Isthmus crude and 20 percent Maya crude, Pemex said.
According to Reuters shipping data and traders, the tanker Maran Penelope reached the port of Yeosu, about 350 kilometres (220 miles) south of Seoul, on March 8. GS Caltex's refinery is in Yeosu.
The purchase was made to procure cheap crude on the spot market and further purchases were likely as long as cheap offers were available, said the spokesman for GS Caltex, a joint venture of GS Holdings and Chevron Corp.
Another 1 million barrels of Mexican crude on board the tanker Ridgebury Lindy B will reach the port city of Daesan, about 100 kilometres southwest of Seoul, later this month, data from Thomson Reuters Oil Research & Forecasts showed.
The city is home to the refining headquarters of Hyundai Oilbank Co Ltd, which declined to comment.
A drop in U.S. crude futures to the lowest in nearly a year against global benchmark Brent opened a trading window for shipments of Latin American crude and U.S. condensate to Asia.
South Korea had not imported crude from Mexico since 1990, when the customs service started its reports.
GS Caltex bought the first condensate cargo shipped from the United States since the easing of a 40-year ban on U.S. oil exports, and also bought 800,000 barrels of Alaskan crude oil, the first U.S. export of Alaskan crude to South Korea in more than a decade. (Additional reporting by Florence Tan in SINGAPORE and Tomas Sarmiento in Mexico City; Editing by Sunil Nair, Ed Davies and Clarence Fernandez)