(Adds details on quarter, share price)
Feb 21 (Reuters) - U.S. oil refiner HollyFrontier Corp's fourth-quarter profit on Wednesday fell short of analysts' estimates on lower than expected margins, sending its shares down as much as five percent.
Chief Financial Officer Richard Voliva said gasoline margins "fell out" in the latter part of the quarter and that the company had not captured the improvement in crude prices in the fourth quarter.
"We had a couple of conversion rate and unit issues during the quarter, which probably hit production and really sales of kind of the higher value of finished products that are the margin," he said.
HollyFrontier, which mostly processes sweet crude oil, said refining margins rose 85 percent to $12.54 per barrel in the quarter.
That was lower, however, than the $13.06 per barrel predicted by Jefferies analyst Corey Goldman and $13.84 estimated by Barclays. Some analysts pointed to technical problems at plants as one reason for the shortfall.
Net profit rose to $521.1 million, or $2.92 per share, in the quarter ended Dec. 31, from $53.2 million, or 30 cents per share, a year earlier, HollyFrontier said in a release.
Excluding items, however, the company reported earnings of 70 cents per share compared to average expectations of 83 cents, according to analysts polled by Thomson Reuters I/B/E/S.
The figures followed results by larger rivals Valero Energy Corp and Marathon Petroleum Corp, which both beat expectations earlier this month in a booming U.S. oil sector.
Operating costs and expenses at the Dallas-based company rose 28 percent to $3.83 billion.
Analysts expect refiners to outshine other energy businesses in 2018 as broadly higher global oil prices drive up U.S. production and they rack up some of the corporate world's biggest gains from recent tax cuts.
Sales and other revenue at HollyFrontier jumped 35 percent to $3.99 billion.
Shares of the company were down 2.5 percent at $44.81 in late morning trade (Reporting by Karan Nagarkatti in Bengaluru; Editing by Shounak Dasgupta)