S-Oil Corp., the No. 3 oil refiner in South Korea, said Thursday that its first-quarter net profit more than doubled from a year earlier, largely thanks to an improvement in its refining business and other areas. 
Net profit reached 433 billion won (US$381 million) in the January-March period, compared with a profit of 211 billion won a year earlier, the company said in a regulatory filing. 
Sales dropped 21.6 % on-year to reach 3.43 trillion won in the first quarter, while it logged an operating income of 491 billion won, compared with an operating income of 238 billion won a year earlier. 
S-Oil said improved cracking margins helped boost its bottom line, with other businesses such as its lubricants unit faring well. 
Its refining business generated an operating income of 220 billion won in the first quarter on sales of 2.47 trillion won. 
S-Oil expects rising demand from Asia will continue to help refiners this year. 
The company's petrochemicals unit posted an operating income of 144 billion won last year, sharply up from an operating income of 46 billion won a year earlier.