Aug 1 (Reuters) - PBF Energy ( PBF ) reported a

bigger-than-expected quarterly loss, driven by heavy turnaround

activity and a weak summer driving season which dented fuel

demand and shrunk refining margins.

PBF's shares slipped 4% to $39.08 on Thursday in premarket

trading.

"Market conditions broke from typical seasonal patterns,

with product cracks higher early in the quarter and declining as

the quarter progressed," PBF Energy's ( PBF ) CEO Matt Lucey said.

The company's gross refining margin dropped more than 40% to

$8.12 per barrel in the second quarter.

Demand for distillate fuels, which include diesel and

heating oil, has been hit sharply this year under pressure from

sluggish manufacturing activity, milder-than-expected winter

weather and booming renewable fuel supply.

The U.S. 3-2-1 spread , a key measure of overall

refining margins in the country fell 19% in the second quarter.

PBF Energy's ( PBF ) crude oil and feedstock throughput also fell

1.5% to 921,300 barrels per day (bpd).

Refining profit was also impacted by heavy turnaround

activity early in the quarter, when margins were the strongest.

"We conducted extensive maintenance in our East,

Mid-continent and West Coast Regions during the first two months

of the quarter," Lucey said.

The company's refinery in Chalmette, Louisiana is expected

to undergo planned maintenance early in the fourth quarter.

PBF Energy ( PBF ) forecast third quarter throughput between 885,000

bpd and 945,000 bpd.

On an adjusted basis, the company lost 54 cents per share in

the second quarter, compared with estimates of a loss of 15

cents per share, according to LSEG data.