X0306 4 2016-09-23 0 0001552000 MPLX LP MPLX 0001344601 Buese Nancy C/O MPLX LP 200 E. HARDIN STREET FINDLAY OH 45840 0 1 0 0 Exec VP and CFO Common Units (Limited Partner Interests) 2016-09-23 4 S 0 10000 32.72 D 187779 D Common Units (Limited Partner Interests) 2016-09-23 4 S 0 5000 33.00 D 182779 D The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on September 8, 2016. The Reporting Person is the Executive Vice President and Chief Financial Officer of MPLX GP LLC, the general partner of the Issuer. The Issuer is managed by the directors and executive officers of MPLX GP LLC. /s/ Molly R. Benson, Attorney-in-Fact for Nancy K. Buese 2016-09-27