ExxonMobil Corp has sold its remaining stake in TonenGeneral Sekiyu KK, Japan's second-largest oil refiner by capacity.

TonenGeneral, formerly a unit of ExxonMobil, bought a controlling stake in itself from ExxonMobil in 2012 in a roughly $4 billion deal, reducing ExxonMobil's stake from 50 percent to 22 percent.

ExxonMobil had gradually reduced its stake in TonenGeneral since then, and had been replaced by Mitsui & Co as the top shareholder in the refiner with a 6.37 percent stake.

The sale will not change TonenGeneral's existing tie-up with ExxonMobil, including brand usage, lubricant oil manufacturing and technical support in refining, the Japanese firm said in a statement.

TonenGeneral also said last Friday it planned to set up a U.S. office in Houston, TX on March 1, to be named TonenGeneral Americas L.L.C., making it the company's fifth overseas base, following the establishment of the TonenGeneral Sekiyu K.K. Singapore branch office in June 2012, Abu Dhabi representative office in November 2013, Doha representative office in March 2015, and the NUC Corporation Shanghai representative office in September 2014.