SUPPLEMENTAL INDENTURE TO BEDELIVERED BY SUBSEQUENT GUARANTORS

Exhibit 4.1

Execution Version

SUPPLEMENTAL INDENTURE

TO BE DELIVERED BY SUBSEQUENT GUARANTORS

SUPPLEMENTAL INDENTURE (this “Supplemental Indenture”), dated as of December 2, 2014, among Tesoro Logistics LP (“TLLP”), Tesoro Logistics Finance Corp., a Delaware corporation (together with TLLP, the “Issuers”), the parties that are signatories hereto as Guarantors (each a “Guaranteeing Subsidiary”) and U.S. Bank National Association, as trustee under the Indenture referred to below (the “Trustee”).

WITNESSETH

WHEREAS, the Issuers have heretofore executed and delivered to the Trustee an indenture (the “Indenture”), dated as of October 29, 2014 providing for the issuance of 5.50% Senior Notes due 2019 (the “2019 Notes”) and the 6.25% Senior Notes due 2022 (the “2022 Notes” and, together with the 2019 Notes, the “Notes”);

WHEREAS, the Indenture provides that under certain circumstances the Guaranteeing Subsidiaries shall execute and deliver to the Trustee a supplemental indenture pursuant to which the Guaranteeing Subsidiaries shall unconditionally guarantee all of the Issuers’ Obligations under the Notes and the Indenture on the terms and conditions set forth herein (the “Note Guarantee”); and

WHEREAS, pursuant to Section 9.01 of the Indenture, the Trustee is authorized to execute and deliver this Supplemental Indenture.

NOW, THEREFORE, in consideration of the foregoing and for other good and valuable consideration, the receipt of which is hereby acknowledged, the Guaranteeing Subsidiaries and the Trustee mutually covenant and agree for the equal and ratable benefit of the Holders of the Notes as follows:

l. CAPITALIZED TERMS. Capitalized terms used herein without definition shall have the meanings assigned to them in the Indenture.

2. AGREEMENT TO GUARANTEE. Each Guaranteeing Subsidiary acknowledges that it has received and reviewed a copy of the Indenture and all other documents it deems necessary to review in order to enter into this Supplemental Indenture, and acknowledges and agrees to (i) join and become a party to the Indenture as indicated by its signature below; (ii) be bound by the Indenture, as of the date hereof, as if made by, and with respect to, each signatory hereto; and (iii) perform all obligations and duties required of a Guarantor pursuant to the Indenture. Each Guaranteeing Subsidiary hereby agrees to provide an unconditional Note Guarantee on the terms and subject to the conditions set forth in the Indenture, including, but not limited to, Article 10 thereof.

3. EXECUTION AND DELIVERY. The Guaranteeing Subsidiaries agree that the Note Guarantees, shall remain in full force and effect notwithstanding the absence of the endorsement of any notation of such Note Guarantees on the Notes.

4. NO RECOURSE AGAINST OTHERS. No past, present or future director, officer, employee, incorporator, stockholder or agent of the Guaranteeing Subsidiaries, as such, shall have any liability for any obligations of the Issuers or any Guaranteeing Subsidiaries under the Notes, any Note Guarantees, the Indenture or this Supplemental Indenture or for any claim based on, in respect of, or by reason of, such obligations or their creation. Each Holder by accepting a Note waives and releases all such liability. The waiver and release are part of the consideration for issuance of the Notes.

5. NEW YORK LAW TO GOVERN. THE LAW OF THE STATE OF NEW YORK SHALL GOVERN AND BE USED TO CONSTRUE THIS SUPPLEMENTAL INDENTURE.

6. COUNTERPARTS. The parties may sign any number of copies of this Supplemental Indenture. Each signed copy shall be an original, but all of them together represent the same agreement. This Supplemental Indenture may be executed in multiple counterparts which, when taken together, shall constitute one instrument. The exchange of copies of this Supplemental Indenture and of signature pages by facsimile or PDF transmissions

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shall constitute effective execution and delivery of this Supplemental Indenture as to the parties hereto and may be used in lieu of the original Supplemental Indenture for all purposes. Signatures of the parties hereto transmitted by facsimile or PDF shall be deemed to be their original signatures for all purposes.

7. EFFECT OF HEADINGS. The Section headings herein are for convenience only and shall not affect the construction hereof.

8. THE TRUSTEE. The Trustee shall not be responsible in any manner whatsoever for or in respect of the validity or sufficiency of this Supplemental Indenture or for or in respect of the recitals contained herein, all of which recitals are made solely by each Guaranteeing Subsidiary and the Issuers.

9. BENEFITS ACKNOWLEDGED. The Guaranteeing Subsidiaries’ Guarantees are subject to the terms and conditions set forth in the Indenture. The Guaranteeing Subsidiaries acknowledge that they will receive direct and indirect benefits from the financing arrangements contemplated by the Indenture and this Supplemental Indenture and that the guarantee and waivers made by it pursuant to the Note Guarantees are knowingly made in contemplation of such benefits.

10. SUCCESSORS. All agreements of the Guaranteeing Subsidiaries in this Supplemental Indenture shall bind its Successors, except as otherwise provided in this Supplemental Indenture. All agreements of the Trustee in this Supplemental Indenture shall bind its successors.

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IN WITNESS WHEREOF, the parties hereto have caused this Supplemental Indenture to be duly executed, all as of the date first above written.

[Signature Page – Supplemental Indenture]