(Reuters) - Refiner HF Sinclair reported a lower second-quarter profit on Thursday as margins slumped due to a tepid summer driving season and a rise in global refining capacity.

The Dallas-based company posted a net income of $151.8 million, or 79 cents per share, in the quarter ending June, compared with $507.7 million, or $2.62 per share, a year earlier.

U.S. refiners ramped up processing capacity to 93.5% in the second quarter, compared with 91% in the same period last year, according to the U.S. Energy Information Administration, on expectations of an uptick in demand that did not materialize.

Fuel demand also came under pressure during the quarter due to lower manufacturing activity and increasing renewable fuel supply.

HF Sinclair's refinery gross margin was $11.33 per barrel in the second quarter, compared with $21.99 a year earlier.

Its refinery utilization averaged 93.6% in the quarter, compared with 81.7%.