X0306 4 2016-09-02 0 0001552000 MPLX LP MPLX 0001510295 Marathon Petroleum Corp 539 S. MAIN STREET FINDLAY OH 45840 1 0 1 0 0001019756 MARKWEST HYDROCARBON L.L.C. 1515 ARAPAHOE STREET TOWER 1, SUITE 1600 DENVER CO 80202 1 0 1 0 0001560713 MPC Investment LLC 539 S. MAIN STREET FINDLAY OH 45840 1 0 1 0 0001683291 MPLX Holdings Inc. 539 S. MAIN ST. FINDLAY OH 45840 1 0 1 0 0001551994 MPLX Logistics Holdings LLC 200 E. HARDIN STREET FINDLAY OH 45840 1 0 1 0 0001551999 MPLX GP LLC 200 E. HARDIN STREET FINDLAY OH 45840 1 0 1 0 Class A Units 2016-09-02 4 D 0 28554313 D 0 I See Footnotes Pursuant to a Master Reorganization Agreement effective September 1, 2016 by and among MPLX Holdings Inc. ("Holdings"), MarkWest Energy Partners, L.P., MWE GP LLC, MPLX LP ("MPLX"), MPLX GP LLC ("the "General Partner"), MPC Investment LLC ("MPC Investment"), MPLX Logistics Holdings LLC ("Logistics Holdings") and MarkWest Hydrocarbon, L.L.C. ("Hydrocarbon"), all issued and outstanding Class A Units representing limited partner interests of MPLX were exchanged for newly issued common units representing limited partner interests of MPLX on a one-to-one conversion, eliminating all issued and outstanding Class A Units representing limited partner interests of MPLX. This Form 4 is filed jointly by Marathon Petroleum Corporation ("MPC"), MPC Investment, the General Partner, Logistics Holdings, Holdings and Hydrocarbon, with respect to the Issuer's Class A Units. The General Partner directly owns 7,193,467 general partner units, representing its 2% general partner interest in the Issuer. MPC Investment owns all of the membership interests or stock in the General Partner, Logistics Holdings and Holdings, and MPC owns all of the membership interests in MPC Investment. Accordingly, MPC, MPC Investment and Holdings may be deemed to have indirectly beneficially owned the securities of the Issuer directly held by the General Partner, Logistics Holdings and Hydrocarbon but disclaim beneficial ownership except to the extent of their respective pecuniary interests therein. /s/ Molly R. Benson, Vice President, Corporate Secretary and Chief Compliance Officer, Marathon Petroleum Corporation 2016-09-06 /s/ Molly R. Benson, Director and Secretary of the Member of MarkWest Hydrocarbon, L.L.C., MPLX Holdings Inc. 2016-09-06 /s/ Molly R. Benson, Vice President, Corporate Secretary and Chief Compliance Officer, MPC Investment LLC 2016-09-06 /s/ Molly R. Benson, Director and Secretary, MPLX Holdings Inc. 2016-09-06 /s/ Molly R. Benson, Assistant Secretary, MPLX Logistics Holdings LLC 2016-09-06 /s/ Molly R. Benson, Vice President and Corporate Secretary, MPLX GP LLC 2016-09-06