US Cash Crude — Grades fall as US supply set to rise, refinery demand slips

HOUSTON, Sept 18 (Reuters) — Grades broadly fell on Friday, dealers said, as domestic output is set to rise while refinery demand weakened. US energy firms this week added rigs for a second week in a row for the first time since July, energy services firm Baker Hughes said in its report on Friday. RIG/U Oil rigs rose by two to 452 this week, their highest since August. US oil refiners are expected to have about 821,000 barrels per day of capacity offline for the week ending September 18, decreasing available refining capacity by 371,000 bpd, research company IIR Energy said. Offline capacity is expected to decrease to 597,000 bpd in the week ending September 25 and to 622,000 bpd in the subsequent week, IIR added. REF/OUT Light Louisiana Sweet for October delivery rose 38 cents to a midpoint of a $4.88 premium and was seen bid and offered between a $4.75 and $5 a barrel premium to US crude futures ​ Mars Sour fell 75 cents to a midpoint of a $2.50 premium and was seen bid and offered between a $2.40 and $2.60 a barrel premium to US crude futures ​ WTI Midland fell 45 cents to a midpoint of a 85-cent premium and was seen bid and offered between a 75-cent and 95-cent a barrel premium