Refining New Zealand's gross margin for July and August rose to $US6.75 a barrel, which the company attributes to its excellent operational performance.
That is a $US7.30 increase over Singapore complex margins and up from just $US3.72 a barrel in May and June.
It has meant the refinery has repaid $NZ13.5 million of support payments to its major shareholders and customers.
The refinery has an agreement with the four major petrol companies who pay top-up payments when the margins fall below a specified floor and who the refinery pays when margins exceed a specified cap.
It said measures taken to improve margins added about 90 cents a barrel in July and August, above the planned 66 cents.
Forsyth Barr analyst Andrew Harvey-Green said he expected the company's margin will be below the floor for the 2014 calendar year.
