US Cash Crude-Grades mixed on second day of volatile roll trade period

Aug 22 (Reuters) - U.S. crude grades were mixed on Friday, on the second day of a volatile roll trading period, dealers said.

Midland firmed 15 cents, while WTI at East Houston (MEH) was flat. Mars eased 20 cents.

Traders use the three-day roll period to adjust their crude slates, square up positions and net out exposures following the expiration of the U.S. crude futures contract.

Prices to roll U.S. crude oil futures positions from September to October traded at a midpoint of 40 cents a barrel.

Meanwhile, West Texas Intermediate crude futures' (WTI) discount to Brent WTCLc1-LCOc1 settled narrower after widening for 8 sessions. A narrowed spread makes U.S. grades less attractive to foreign buyers.

Baker Hughes said oil rig counts, an indicator of future output, fell by one to 411 this week.

In refining news, Phillips 66's PSX.N 356,000 barrels-per-day Wood River refinery in Illinois had issues with its crude unit, trading sources said on Friday.

U.S. oil refiners are expected to have about 453,000 barrels per day of capacity offline in the week ending August 22, decreasing available refining capacity by 202,000 bpd, research company IIR Energy said on Friday.

* Light Louisiana Sweet WTC-LLS for September delivery firmed 20 cents to a midpoint of a $1.75 premium and was seen bid and offered between a $1.50 and $2.00 a barrel premium to U.S. crude futures CLc1

* Mars Sour WTC-MRS eased 20 cents to a midpoint of a 25-cent discount and was seen bid and offered between discount of 50 cents and parity to U.S. crude futures CLc1

* WTI Midland WTC-WTM firmed 15 cents to a midpoint of a $1 premium and was seen bid and offered between a 80-cent and $1.20 a barrel premium to U.S. crude futures CLc1

* West Texas Sour WTC-WTS gained 5 cents at a midpoint of a 20-cent premium and was seen bid and offered between parity and 40-cent a barrel premium to U.S. crude futures CLc1

* WTI at East Houston WTC-MEH, also known as MEH, traded between a $1.20 and $1.50 a barrel premium to U.S. crude futures CLc1

* ICE Brent October futures LCOc1 rose 6 cents to settle at $67.73 a barrel on Friday.

* WTI October crude CLc1 futures rose 14 cents to settle at $63.66 a barrel on Friday.

* The Brent/WTI spread WTCLc1-LCOc1 narrowed 11 cents to to last trade at minus $4.04, after hitting a high of minus $4.03 and a low of minus $4.13.