MPLX (MPLX) legal chief reports unit grant and tax dispositions

Rhea-AI Filing Summary

MPLX LP insider Molly R. Benson, Chief Legal Officer and Corporate Secretary, reported equity compensation activity in common units. On March 1, she acquired 8,803 units as a grant at $0.0000 per unit. On March 2, she disposed of 614, 1,240, and 998 units at $59.22 per unit through tax-withholding dispositions to cover tax liabilities, leaving 46,114 units held directly.

SEC Form 4

FORM 4

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
or Section 30(h) of the Investment Company Act of 1940

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

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Benson Molly R

(Last) (First) (Middle)

C/O MPLX LP

200 E. HARDIN STREET

(Street)

FINDLAY OH 45840

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
MPLX LP [ MPLX ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	Chief Legal Ofc & Corp Sec

3. Date of Earliest Transaction (Month/Day/Year)
03/01/2026

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	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
Common Units (Limited Partner Interests)	03/01/2026		A		8,803	A	$0	48,966	D
Common Units (Limited Partner Interests)	03/02/2026		F		614	D	$59.22	48,352	D
Common Units (Limited Partner Interests)	03/02/2026		F		1,240	D	$59.22	47,112	D
Common Units (Limited Partner Interests)	03/02/2026		F		998	D	$59.22	46,114	D

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 (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	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 (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (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: 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

Explanation of Responses:

Remarks:

The Reporting Person is the Chief Legal Officer and Corporate Secretary of MPLX GP LLC, the general partner of the Issuer. The Issuer is managed by the directors and executive officers of MPLX GP LLC.

	/s/ Shane T. Pfleiderer, Attorney-in-Fact for Molly R. Benson	03/03/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
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FAQ

What insider transactions did Molly R. Benson report for MPLX on this Form 4?

Molly R. Benson reported receiving a grant of 8,803 MPLX common units on March 1 and three tax-withholding dispositions totaling 2,852 units on March 2 at $59.22 per unit, reflecting equity compensation and related tax payments.

Was the MPLX insider activity a stock sale or tax withholding event?

The MPLX insider activity was a tax-withholding disposition, not an open-market sale. Code F transactions indicate units were surrendered to cover tax liabilities related to equity compensation, rather than discretionary selling into the market.

How many MPLX units does Molly R. Benson hold after these transactions?

After the reported transactions, Molly R. Benson holds 46,114 MPLX common units directly. This figure reflects the 8,803-unit grant she received and the 2,852 units surrendered for tax withholding across the three Form 4 line items.

What price was used for the MPLX tax-withholding dispositions on this Form 4?

Each tax-withholding disposition of MPLX common units was valued at $59.22 per unit. This price was applied to the 614, 1,240, and 998 units delivered to satisfy tax obligations arising from the equity award.

What do the transaction codes A and F mean in the MPLX Form 4 filing?

In this MPLX Form 4, code A identifies a grant or award acquisition of 8,803 units, while code F indicates tax-withholding dispositions, where 614, 1,240, and 998 units were delivered to cover exercise price or tax liabilities.

What role does Molly R. Benson hold at MPLX related to this Form 4?

Molly R. Benson is identified as Chief Legal Officer and Corporate Secretary of MPLX. The Form 4 shows her direct ownership transactions in MPLX common units tied to equity compensation awards and associated tax-withholding events.