US Cash Crude-Grades mixed on the first day of the roll period

HOUSTON, Jan 20 (Reuters) - Grades were mixed on Tuesday, dealers said, on the first day of the volatile roll trading period.

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 February to March traded at minus 20 cents a barrel.

The spread between WTI and Brent narrowed to settle at $4.56. A spread larger than minus $4 typically encourages export demand.

• Light Louisiana Sweet for February delivery eased 35 cents to a midpoint of a $1.65 premium and was seen bid and offered between a $1.00 and $2.30 a barrel premium to U.S. crude futures. CLc1 ​

• Mars Sour firmed 25 cents to a midpoint of a parity and was seen bid and offered between a discount of 20 cents​​ and 20-cent a barrel premium to U.S. crude futures CLc1 ​

• WTI Midland eased 15 cents to a midpoint of a 95-cent premium and was seen bid and offered between an 80-cent and $1.10 a barrel premium to U.S. crude futures CLc1 ​

• West Texas Sour eased 70 cents to a midpoint of a $2.85 discount and was seen bid and offered between a $3.00 and $2.70 a barrel discount to U.S. crude futures CLc1 ​

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

• ICE Brent March futures LCOc1 remained unchanged at $64.92 a barrel on Tuesday​.

• WTI March crude CLc1 futures fell 79 cents, currently trading at $59.57 a barrel on Tuesday​

• The Brent/WTI spread narrowed to last trade at minus $4.56, after hitting a high of minus $4.40 and a low of minus $4.72