X0306 4 2018-10-01 0 0001552000 MPLX LP MPLX 0001331928 Heminger Gary R. C/O MPLX LP 200 E. HARDIN STREET FINDLAY OH 45840 1 1 0 0 Chairman, CEO Common Units (Limited Partner Interests) 2018-10-01 4 F 0 6061 35.24 D 190438 D Common Units (Limited Partner Interests) 2018-10-01 4 F 0 9227 35.24 D 181211 D Common Units (Limited Partner Interests) 2018-10-01 4 F 0 16968 35.24 D 164243 D Common Units (Limited Partner Interests) 26750 I By Revocable Trust Common Units (Limited Partner Interests) 1576.612 I As UTMA custodian for minor grandchild 1 Common Units (Limited Partner Interests) 1576.612 I As UTMA custodian for minor grandchild 2 Common Units (Limited Partner Interests) 1576.612 I As UTMA custodian for minor grandchild 3 Common Units (Limited Partner Interests) 1576.612 I As UTMA custodian for minor grandchild 4 Common Units (Limited Partner Interests) 1576.612 I As UTMA custodian for minor grandchild 5 Common Units (Limited Partner Interests) 1500 I As UTMA custodian for minor grandchild 6 By Gary R. Heminger Revocable Trust. The reporting person disclaims beneficial ownership of these units, and this report shall not be deemed an admission that the reporting person is the beneficial owner of such securities for purposes of Section 16 or for any other purpose. The units are held in UTMA accounts for the benefit of Mr. Heminger's minor grandchildren. Mr. Heminger is the custodian and maintains investment control over the accounts. Total includes 76.612 units resulting from automatic distribution reinvestment pursuant to the terms of a UTMA account. The Reporting Person is the Chairman of the Board of Directors and the Chief Executive 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 Gary R. Heminger 2018-10-03