US Cash Crude-Grades mixed on final day of roll trade 

HOUSTON, Oct 23 (Reuters) - Grades were mixed on the third and final day of the volatile roll-trading period, dealers said.

The roll-trade period is used by traders to square positions, adjust slates and net out any exposure. Prices to roll positions from November to December traded at $3.50 a barrel.

US energy firms this week raised the oil rig count by one to 460, the highest since early October, energy services firm Baker Hughes BKR.O said in its closely followed report on Friday. RIG/U

• Light Louisiana Sweet for November delivery was steady at a midpoint of a $6.90 premium and was seen bid and offered between a $6.80 and a $7.00 a barrel premium to US crude futures ​

• Mars Sour fell $1 to a midpoint of a $9 premium and was seen bid and offered between an $8.00 and a $10 a barrel premium to US crude futures ​

• WTI Midland rose 65 cents to a midpoint of a $1.45 premium and was seen bid and offered between a $1.35 and a $1.55 a barrel premium to US crude futures ​

• West Texas Sour fell 28 cents to a midpoint of a $3.08 discount and was seen bid and offered between a $3.45 and $2.70 a barrel discount to US crude futures ​

• WTI at East Houston , also known as MEH, traded between a $1.70 and $1.90 a barrel premium to US crude futures ​

• ICE Brent December futures rose $3.55 to settle at $116.72 a barrel on Friday.

• WTI December crude futures rose $3.8 to settle at $103.27 a barrel on Friday.

• The Brent/WTI spread narrowed 28 cents to last trade at minus $13.42, after hitting a high of minus $13.15 and a low of minus $14.30.