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Investments and Noncontrolling Interests (Schedule of Equity Method Investments) (Details) - USD ($)
$ in Millions

3 Months Ended

Mar. 31, 2025

Mar. 31, 2024

Dec. 31, 2024

Schedule of Equity Method Investments

Equity method investments

$ 4,751

$ 4,531

Investments - redemptions, repayments, return of capital and sales proceeds

21

$ 0

Contribution of Net Assets

115

^[1]

$ 0

MarkWest EMG Jefferson Dry Gas Gathering Company, L.L.C(3)

Schedule of Equity Method Investments

Investments - redemptions, repayments, return of capital and sales proceeds

21

Contribution of Property

125

Crude Oil and Products Logistics

Schedule of Equity Method Investments

Equity method investments

$ 1,606

1,595

Crude Oil and Products Logistics | Illinois Extension Pipeline Company, L.L.C.

Schedule of Equity Method Investments

Equity method investment, ownership percentage

35.00%

Equity method investments

$ 225

218

Crude Oil and Products Logistics | LOOP LLC

Schedule of Equity Method Investments

Equity method investment, ownership percentage

41.00%

Equity method investments

$ 314

310

Crude Oil and Products Logistics | MarEn Bakken Company LLC(1)

Schedule of Equity Method Investments

Equity method investment, ownership percentage

25.00%

Equity method investments

^[2]

$ 521

526

Crude Oil and Products Logistics | Other VIEs and Non-VIEs

Schedule of Equity Method Investments

Equity method investments

^[3]

$ 546

541

Crude Oil and Products Logistics | Indirect Ownership Interest [Member] | Bakken Pipeline System [Member]

Schedule of Equity Method Investments

Equity method investment, ownership percentage

9.19%

Natural Gas and NGL Services

Schedule of Equity Method Investments

Equity method investments

$ 3,145

2,936

Natural Gas and NGL Services | BANGL, LLC

Schedule of Equity Method Investments

Equity method investment, ownership percentage

45.00%

Equity method investments

$ 279

281

Natural Gas and NGL Services | MarkWest EMG Jefferson Dry Gas Gathering Company, L.L.C(3)

Schedule of Equity Method Investments

Equity method investment, ownership percentage

67.00%

Equity method investments

$ 428

^[4]

329

Natural Gas and NGL Services | MarkWest Utica EMG, L.L.C.

Schedule of Equity Method Investments

Equity method investment, ownership percentage

60.00%

Equity method investments

$ 782

742

Natural Gas and NGL Services | Ohio Gathering Company L.L.C.

Schedule of Equity Method Investments

Equity method investment, ownership percentage

34.00%

Equity method investments

^[5]

$ 464

470

Natural Gas and NGL Services | Sherwood Midstream LLC

Schedule of Equity Method Investments

Equity method investment, ownership percentage

50.00%

Equity method investments

$ 485

488

Natural Gas and NGL Services | WPC Parent, LLC

Schedule of Equity Method Investments

Equity method investment, ownership percentage

30.00%

Equity method investments

$ 243

208

Natural Gas and NGL Services | Other VIEs and Non-VIEs

Schedule of Equity Method Investments

Equity method investments

^[3]

$ 464

$ 418

Natural Gas and NGL Services | Indirect Ownership Interest [Member] | Ohio Gathering Company L.L.C.

Schedule of Equity Method Investments

Equity method investment, ownership percentage

39.00%

[1]	(1)    Represents the book value of assets contributed by MPLX to a joint venture.
[2]	The investment in MarEn Bakken Company LLC includes our 9.19 percent indirect interest in a joint venture (“Dakota Access”) that owns and operates the Dakota Access Pipeline and Energy Transfer Crude Oil Pipeline projects (collectively, the “Bakken Pipeline system”).
[3]	Some investments included within Other have also been deemed to be VIEs.
[4]	On March 31, 2025, MPLX contributed a 100 percent owned subsidiary with a fair value of $125 million to MarkWest EMG Jefferson Dry Gas Gathering Company, L.L.C. MPLX received a special distribution of $21 million as a result of the transaction, which is reflected as a return of capital on the consolidated statement of cash flows.
[5]	MPLX also holds a 39 percent indirect interest in OGC through our ownership interest in MarkWest Utica EMG, L.L.C.

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