Oct 31 (Reuters) - Refiner HF Sinclair reported

a loss in third-quarter profit on Thursday, hurt by a slump in

margins, especially in the West and Mid-Continent regions, due

to an oversupply.

The Dallas-based company posted a loss of $75.9 million, or

40 cents per share, in the quarter ending September, compared

with net income of $790.9 million, or $4.23 per share, a year

earlier.