Exhibit 8.01

SIDLEY AUSTIN LLP 1000 LOUISIANA STREET SUITE 6000 HOUSTON, TX 77002 +1 713 495 4500 +1 713 495 7799 FAX   AMERICA  •  ASIA PACIFIC  •  EUROPE

July 2, 2019

NuStar Energy, L.P.

19003 IH-10 West

San Antonio, Texas 78257

Re: Registration Statement on Form S-3

Ladies and Gentlemen:

We have acted as special tax counsel to NuStar Energy, L.P., a Delaware limited partnership (the “Partnership”), in connection with the registration statement on Form S-3 (the “Registration Statement”), being filed by the Partnership with the Securities and Exchange Commission (the “SEC”) pursuant to the Securities Act of 1933, as amended (the “Securities Act”), relating to the registration of common and preferred units representing limited partner interests in the Partnership and debt securities of NuStar Logistics, L.P., a Delaware limited partnership, that may be offered and sold from time to time pursuant to Rule 415 under the Securities Act.

This opinion is based on various facts and assumptions, and is conditioned upon certain representations made to us by the Partnership as to factual matters through an officer’s certificate (the “Officer’s Certificate”). In addition, this opinion is based upon the factual representations of the Partnership concerning its business, properties and governing documents as set forth in the Registration Statement and the Partnership’s responses to our examinations and inquiries.

In our capacity as special tax counsel to the Partnership, we have made such legal and factual examinations and inquiries, including an examination of originals or copies certified or otherwise identified to our satisfaction of such documents, corporate records and other instruments, as we have deemed necessary or appropriate for purposes of this opinion. In our examination, we have assumed the authenticity of all documents submitted to us as originals, the genuineness of all signatures thereon, the legal capacity of natural persons executing such documents and the conformity to authentic original documents of all documents submitted to us as copies. For the purpose of our opinion, we have not made an independent investigation or audit of the facts set forth in the above-referenced documents or in the Officer’s Certificate. In addition, in rendering this opinion we have assumed the truth and accuracy of all representations and statements made to us which are qualified as to knowledge or belief, without regard to such qualification.

We are opining herein as to the effect on the subject transactions only of the federal income tax laws of the United States and we express no opinion with respect to the applicability thereto, or the effect thereon, of other federal laws, foreign laws, the laws of any state or any other jurisdiction or as to any matters of municipal law or the laws of any other local agencies within any state. No opinion is expressed as to any matter not discussed herein.

Based on such facts, assumptions and representations and subject to the limitations set forth herein and in the Registration Statement and the Officer’s Certificate, the statements in the Registration Statement under the heading “Material Tax Consequences” insofar as such statements purport to constitute summaries of United States federal income tax law and regulations or legal conclusions with respect thereto, constitute the opinion of Sidley Austin LLP as to the material United States federal income tax consequences of the matters described therein.

Sidley Austin LLP is a limited liability partnership practicing in affiliation with other Sidley Austin partnerships.

This opinion is rendered to you as of the date hereof, and we undertake no obligation to update this opinion subsequent to the date hereof. This opinion is based on various statutory provisions, regulations promulgated thereunder and interpretations thereof by the Internal Revenue Service and the courts having jurisdiction over such matters, all of which are subject to change either prospectively or retroactively. Also, any variation or difference in the facts from those set forth in the representations described above, including in the Registration Statement and the Officer’s Certificate, may affect the conclusions stated herein.

This opinion is furnished to you, and is for your use in connection with the transactions set forth in the Registration Statement. This opinion may not be relied upon by you for any other purpose or furnished to, assigned to, quoted to or relied upon by any other person, firm or other entity, for any purpose, without our prior written consent, except that this opinion may be relied upon by persons entitled to rely on it pursuant to applicable provisions of federal securities law.

We hereby consent to the filing of this opinion as an exhibit to the Registration Statement and to the incorporation by reference of this opinion to the Registration Statement. In giving such consent, we do not thereby admit that we are within the category of persons whose consent is required under Section 7 of the Securities Act or the rules or regulations of the SEC promulgated thereunder.

Very truly yours,

/s/ Sidley Austin LLP