More on Marathon Petroleum's (MPC) Q1 results: Refining and marketing segment's operating profit climbed 17% to $1.11B. Operating margin edged up to 5% from 4.7%. Refinery throughput rose to 1.67M bbl/day from 1.32M bbl/day in the year-ago quarter. Sales volume rose to 1.88M bbl/day from 1.53M. Shares +0.7% premarket.