MPLX LP

12. Debt

MPLX’s outstanding borrowings consist of the following:

Credit Agreement

MPLX’s credit agreement (the “MPLX Credit Agreement”) matures in July 2027 and, among other things, provides for a $2.0 billion unsecured revolving credit facility and letter of credit issuing capacity under the facility of up to $150 million. Letter of credit issuing capacity is included in, not in addition to, the $2.0 billion borrowing capacity. Borrowings under the MPLX Credit Agreement bear interest, at MPLX’s election, at either the Adjusted Term SOFR or the Alternate Base Rate, both as defined in the MPLX Credit Agreement, plus an applicable margin.

At June 30, 2025, MPLX hadno outstanding borrowings and less than $1 million in letters of credit outstanding under the MPLX Credit Agreement, resulting in total availability of approximately $2.0 billion.

Fixed Rate Senior Notes

MPLX’s senior notes, including those issued by consolidated subsidiaries, consist of various series of senior notes maturing between 2026 and 2058 with interest rates ranging from 1.750 percent to 5.950 percent. Interest on each series of notes is payable semi-annually in arrears on various dates depending on the series of the notes.

On February 18, 2025, MPLX repaid all of MPLX’s outstanding $500 million aggregate principal amount of 4.000 percent senior notes due February 2025 at maturity.

On March 10, 2025, MPLX issued $1.0 billion aggregate principal amount of 5.400 percent senior notes due 2035 (the “2035 Senior Notes”) and $1.0 billion aggregate principal amount of 5.950 percent senior notes due 2055 (the “2055 Senior Notes”) in an underwritten public offering. The 2035 Senior Notes and 2055 Senior Notes were offered at prices to the public of 99.398 percent of par and 98.331 percent of par, respectively, each with interest payable semi-annually in arrears, commencing on October 1, 2025. On April 9, 2025, MPLX used $1.2 billion of the net proceeds from the issuance of the 2035 Senior Notes and 2055 Senior Notes to redeem all of (i) MPLX’s outstanding $1,189 million aggregate principal amount of 4.875 percent senior notes due June 2025 and (ii) MarkWest’s outstanding $11 million aggregate principal amount of 4.875 percent senior notes due June 2025. MPLX intends to use the remaining net proceeds for general partnership purposes.