X0306 4 2015-12-04 0 0001552000 MPLX LP MPLX 0001510295 Marathon Petroleum Corp 539 S. MAIN STREET FINDLAY OH 45840 1 0 1 0 0001560713 MPC Investment LLC 539 S. MAIN STREET FINDLAY OH 45840 1 0 1 0 0001551999 MPLX GP LLC 200 E. HARDIN STREET FINDLAY OH 45840 1 0 0 0 0001551994 MPLX Logistics Holdings LLC 200 E. HARDIN STREET FINDLAY OH 45840 0 0 1 0 Class A Units 2015-12-04 4 A 0 28554313 A 28554313 I See Footnotes This Form 4 is filed jointly by Marathon Petroleum Corporation ("MPC"), MPC Investment LLC ("MPC Investment"), MPLX GP LLC (the "General Partner"), and MPLX Logistics Holdings LLC ("MPLX Logistics Holdings"), with respect to the Issuer's Class A units. MarkWest Hydrocarbon, Inc., an indirect wholly-owned subsidiary of the Issuer, owns all of the Issuer's Class A units. The General Partner directly owns 6,800,475 general partner units, representing its 2% general partner interest in the Issuer and MPLX Logistics Holdings LLC beneficially owns 56,932,134 common units representing limited partnership interests in the Issuer. MPC Investment, a direct wholly-owned subsidiary of MPC, owns all of the membership interests in both the General Partner and MPLX Logistics Holdings. Accordingly, the General Partner and MPLX Logistics Holdings are both indirect wholly-owned subsidiaries of MPC. MPC Investment owns all of the membership interests in both the General Partner and MPLX Logistics Holdings, and MPC owns all of the membership interest in MPC Investment. Accordingly, MPC, MPC Investment, the General Partner and MPLX Logistics Holdings may be deemed to indirectly beneficially own the securities of the Issuer directly held by MarkWest Hydrocarbon, Inc., but disclaim beneficial ownership except to the extent of their respective pecuniary interests therein. Received in exchange for 22,640,000 MarkWest Energy Partners, L.P. ("MarkWest") Class A units in connection with the merger of Sapphire Holdco LLC, a wholly-owned subsidiary of the Issuer, with and into MarkWest on December 4, 2015, with MarkWest as the surviving entity (the "Merger"). The MarkWest Class A units outstanding immediately prior to the effective time of the Merger were converted into the specified number of Issuer Class A units having substantially similar rights and obligations that the MarkWest Class A units had immediately prior to the effective time. /s/ J. Michael Wilder, Vice President, General Counsel and Secretary, Marathon Petroleum Corporation 2015-12-08 /s/ J. Michael Wilder, Vice President, General Counsel and Secretary, MPC Investment LLC 2015-12-08 /s/ Molly R. Benson, Assistant Secretary, MPLX GP LLC 2015-12-08 /s/ Molly R. Benson, Assistant Secretary, MPLX Logistics Holdings LLC 2015-12-08