Sec Form 4 Filing - Marathon Petroleum Corp @ MPLX LP - 2015-12-04

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Marathon Petroleum Corp 2. Issuer Name and Ticker or Trading Symbol MPLX LP [ MPLX] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 539 S. MAIN STREET 3. Date of Earliest Transaction (MM/DD/YY) 12/04/2015 (Street) FINDLAY, OH45840 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Class A Units 12/04/2015 A 28,554,313 ( 1 ) ( 2 ) ( 3 ) ( 4 ) ( 5 ) A 28,554,313 I See Footnotes ( 1 ) ( 2 ) ( 3 ) ( 4 ) ( 5 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Marathon Petroleum Corp 539 S. MAIN STREET FINDLAY, OH45840 X X MPC Investment LLC 539 S. MAIN STREET FINDLAY, OH45840 X X MPLX GP LLC 200 E. HARDIN STREET FINDLAY, OH45840 X MPLX Logistics Holdings LLC 200 E. HARDIN STREET FINDLAY, OH45840 X Signatures /s/ J. Michael Wilder, Vice President, General Counsel and Secretary, Marathon Petroleum Corporation 12/08/2015 Signature of Reporting Person Date /s/ J. Michael Wilder, Vice President, General Counsel and Secretary, MPC Investment LLC 12/08/2015 Signature of Reporting Person Date /s/ Molly R. Benson, Assistant Secretary, MPLX GP LLC 12/08/2015 Signature of Reporting Person Date /s/ Molly R. Benson, Assistant Secretary, MPLX Logistics Holdings LLC 12/08/2015 Signature of Reporting Person Date

Explanation of Responses:

( 1 )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. ( 2 )MarkWest Hydrocarbon, Inc., an indirect wholly-owned subsidiary of the Issuer, owns all of the Issuer's Class A units. ( 3 )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. ( 4 )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. ( 5 )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.

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