May 1 (Reuters) - U.S. refiner HF Sinclair ( DINO )

posted a smaller-than-expected loss in the first quarter on

Thursday, supported by sequential improvement in refining

margins.

The Dallas, Texas-based company posted an adjusted loss of

27 cents per share during the January-March quarter, compared

with analysts' average estimate of 44 cents per share loss,

according to data compiled by LSEG.