HF Sinclair : 2023 Joint Proxy Statement/Prospectus

MERGER PROPOSAL-YOUR VOTE IS VERY IMPORTANT

To the Stockholders of HF Sinclair Corporation and the Unitholders of Holly Energy Partners, L.P.:

On August 15, 2023, HF Sinclair Corporation ("HF Sinclair") and Holly Energy Partners, L.P. ("HEP") entered into an Agreement and Plan of Merger (as the same may be amended or supplemented from time to time, the "Merger Agreement") with Holly Logistic Services, L.L.C. (the "General Partner"), the general partner of HEP Logistics Holdings, L.P. ("HLH"); HLH, the general partner of HEP; Navajo Pipeline Co., L.P., an indirect wholly owned subsidiary of HF Sinclair ("HoldCo"); and Holly Apple Holdings LLC, a wholly owned subsidiary of HoldCo ("Merger Sub"); pursuant to which Merger Sub will merge with and into HEP (the "Merger"), with HEP surviving as an indirect wholly owned subsidiary of HF Sinclair.

Under the terms of the Merger Agreement, if the Merger is completed, at the effective time of the Merger (the "Effective Time"), each outstanding common unit representing a limited partner interest in HEP (each, a "HEP Common Unit") other than the HEP Common Units already owned by HF Sinclair and its subsidiaries, including HoldCo, will be converted into the right to receive (i) 0.315 (the "Exchange Ratio") shares of common stock, par value $0.01 per share, of HF Sinclair (the "HF Sinclair Common Stock"), with cash paid in lieu of the issuance of fractional shares, if any, and (ii) $4.00 in cash, without interest (the "Cash Consideration" and, together with the shares of HF Sinclair Common Stock to be issued in the Merger, the "Merger Consideration"). Existing stockholders of HF Sinclair ("HF Sinclair Stockholders") will continue to own their existing HF Sinclair Common Stock. Upon the closing of the Merger, former holders of HEP Common Units ("HEP Unitholders") and existing HF Sinclair Stockholders will own approximately 10% and 90%, respectively, of the HF Sinclair Common Stock.

In connection with the Merger, (i) HLH's non-economic general partner interest in HEP, (ii) HLH's special general partner interest in HEP (the "Special General Partner Interest"), and (iii) the HEP Common Units owned by HF Sinclair and its subsidiaries, including HoldCo, will not be cancelled, will not be converted into the Merger Consideration and will remain outstanding following the Merger as a non-economic general partner interest in HEP, a Special General Partner Interest in HEP and as HEP Common Units, respectively.

In connection with the Merger, HF Sinclair will hold a special meeting of its stockholders (as the same may be adjourned or postponed, the "HF Sinclair Special Meeting") and HEP will hold a special meeting of its unitholders (as the same may be adjourned or postponed, the "HEP Special Meeting").

At the HF Sinclair Special Meeting, the HF Sinclair Stockholders will be asked to consider and vote on proposals to (i) approve the issuance of shares of HF Sinclair Common Stock to HEP Unitholders pursuant to the Merger Agreement (the "HF Sinclair Stock Issuance Proposal") and (ii) approve the adjournment of the HF Sinclair Special Meeting to a later date or dates, if necessary or appropriate, to solicit additional proxies in the event there are not sufficient votes at the time of the HF Sinclair Special Meeting to approve the HF Sinclair Stock Issuance Proposal (the "HF Sinclair Adjournment Proposal"). The approval by the HF Sinclair Stockholders of the HF Sinclair Stock Issuance Proposal is required by New York Stock Exchange ("NYSE") rules relating to issuances of securities to certain related parties.

The conflicts committee (the "HF Sinclair Conflicts Committee") of the board of directors of HF Sinclair (the "HF Sinclair Board") and the HF Sinclair Board have unanimously approved the Merger Agreement and recommend that HF Sinclair Stockholders vote "FOR" the HF Sinclair Stock Issuance Proposal. The HF Sinclair Board recommends that HF Sinclair Stockholders vote

"FOR" the HF Sinclair Adjournment Proposal. The HF Sinclair Stockholders should be aware that certain of the directors, executive officers and other affiliates of HF Sinclair may have interests in the Merger that are different from, or in addition to, the interests they may have as a HF Sinclair Stockholder. See "Special Factors-Interests of Certain Persons in the Merger."

At the HEP Special Meeting, the HEP Unitholders will be asked to consider and vote on proposals to (i) approve the Merger Agreement and the transactions contemplated thereby (the "Merger Proposal") and (ii) approve the adjournment of the HEP Special Meeting to a later date or dates, if necessary or appropriate, to solicit additional proxies in the event there are not sufficient votes at the time of the HEP Special Meeting to approve the Merger Proposal (the "HEP Adjournment Proposal"). Pursuant to the Merger Agreement, HF Sinclair has agreed that it will vote, or cause to be voted, all HEP Common Units then owned beneficially or of record by HF Sinclair or any of its subsidiaries in favor of the Merger Proposal. HF Sinclair currently holds approximately 47% of the issued and outstanding HEP Common Units through its subsidiaries, along with the non-economic general partner interest and the Special General Partner Interest.

The conflicts committee of the board of directors of the General Partner (the "HEP Conflicts Committee") as well as the board of directors of the General Partner have unanimously and in good faith approved the Merger Agreement and recommend that HEP Unitholders vote "FOR" the Merger Proposal. The board of directors of the General Partner also recommends that HEP Unitholders vote "FOR" the HEP Adjournment Proposal. The HEP Unitholders should be aware that certain of the directors, executive officers and other affiliates of the General Partner and certain members of the HEP Conflicts Committee may have interests in the Merger that are different from, or in addition to, the interests they may have as a HEP Unitholder. See "Special Factors-Interests of Certain Persons in the Merger."

Although the number of shares of HF Sinclair Common Stock that HEP Unitholders will receive in exchange for their HEP Common Units is fixed, the market value of the Merger Consideration will fluctuate with the market price of HF Sinclair Common Stock and will not be known at the time HEP Unitholders vote on the Merger Proposal or at the time HF Sinclair Stockholders vote on the HF Sinclair Stock Issuance Proposal. Based on the closing price of HF Sinclair Common Stock on the NYSE on August 15, 2023, the last trading day before the public announcement of the parties entering into the Merger Agreement, the Exchange Ratio represented approximately $17.71 in value for each HEP Common Unit for total Merger Consideration of $21.71 for each HEP Common Unit. Based on the closing price of HF Sinclair Common Stock on the NYSE on October 23, 2023, the most recent practicable day before the printing of the accompanying joint proxy statement/prospectus, the Exchange Ratio represented approximately $17.50 in value for each HEP Common Unit for a total Merger Consideration of $21.50 for each HEP Common Unit. We urge you to obtain current market quotations for HF Sinclair Common Stock (trading symbol "DINO") and HEP Common Units (trading symbol "HEP").

We cannot complete the Merger unless the HF Sinclair Stockholders approve the HF Sinclair Stock Issuance Proposal and the HEP Unitholders approve the Merger Proposal. Accordingly, your vote is very important regardless of the number of shares of HF Sinclair Common Stock or HEP Common Units you own. Voting instructions are set forth inside this joint proxy statement/prospectus.

The obligations of HF Sinclair and HEP to complete the Merger are subject to the satisfaction or waiver of a number of conditions set forth in the Merger Agreement, a copy of which is attached as Annex Ato the accompanying joint proxy statement/prospectus. The accompanying joint proxy statement/prospectus describes the HF Sinclair Special Meeting and the proposals to be considered thereat, the HEP Special Meeting and the proposals to be considered thereat, the Merger and the documents and agreements related to the Merger. It also contains or incorporates by reference information about HF Sinclair and HEP and certain related agreements and matters. Please carefully read the entire accompanying joint proxy statement/prospectus, including "Risk Factors" beginning on page 22, for a discussion of the risks relating to the proposed Merger. You also can obtain information about HF Sinclair and HEP from documents that each has filed with the

U.S. Securities and Exchange Commission. Please see "Where You Can Find More Information" beginning on page 184 of the accompanying joint proxy statement/prospectus for how you may obtain such information.

Sincerely,

Franklin Myers

Chairperson of the Board of Directors HF Sinclair Corporation

Michael C. Jennings

Chairperson of the Board of Directors Holly Logistic Services, L.L.C.,

the general partner of HEP Logistics Holdings, L.P., which is the general partner of Holly Energy Partners, L.P.

Neither the U.S. Securities and Exchange Commission nor any state securities commission has approved or disapproved of the securities to be issued in connection with the Merger described in the accompanying joint proxy statement/prospectus or determined that the accompanying joint proxy statement/prospectus is accurate or complete. Any representation to the contrary is a criminal offense.

The accompanying document is dated October 26, 2023 and is first being mailed to the HF Sinclair Stockholders and HEP Unitholders on or about October 26, 2023.

Dallas, Texas

October 26, 2023

HF Sinclair Corporation

2828 N. Harwood, Suite 1300

Dallas, Texas 75201

NOTICE OF VIRTUAL SPECIAL MEETING OF STOCKHOLDERS

To the Stockholders of HF Sinclair Corporation:

You are cordially invited to attend the virtual special meeting (as the same may be adjourned or postponed, the "HF Sinclair Special Meeting") of stockholders of HF Sinclair Corporation ("HF Sinclair"), which will be held exclusively via a live audio webcast on November 28, 2023 at 9:30 a.m., Central Time, at https://www.virtualshareholdermeeting.com/DINO2023SM, for the following purposes:

• to vote on a proposal (the "HF Sinclair Stock Issuance Proposal") to approve the issuance of shares of common stock, par value $0.01 per share, of HF Sinclair ("HF Sinclair Common Stock" and such issuance, the "HF Sinclair Stock Issuance") pursuant to the Agreement and Plan of Merger (as the same may be amended or supplemented from time to time, the "Merger Agreement"), dated as of August 15, 2023, by and among HF Sinclair, Navajo Pipeline Co., L.P. ("HoldCo"), Holly Apple Holdings LLC ("Merger Sub"), HEP Logistics Holdings, L.P. ("HLH"), Holly Logistic Services, L.L.C. (the "General Partner") and Holly Energy Partners, L.P. ("HEP"); and
• to vote on a proposal to approve the adjournment of the HF Sinclair Special Meeting to a later date or dates, if necessary or appropriate, to solicit additional proxies in the event there are not sufficient votes at the time of the HF Sinclair Special Meeting to approve the above proposal (the "HF Sinclair Adjournment Proposal").

The HF Sinclair Special Meeting will be held via a live audio webcast in a virtual meeting format at https://www.virtualshareholdermeeting.com/DINO2023SM. Holders of HF Sinclair Common Stock (the "HF Sinclair Stockholders") will not be able to attend the HF Sinclair Special Meeting physically in-person. The accompanying joint proxy statement/prospectus includes instructions on how to access the virtual HF Sinclair Special Meeting and how to participate and vote from home or any remote location with Internet connectivity. You or your proxy holder will be able to virtually attend and vote at the virtual HF Sinclair Special Meeting by visiting https://www.virtualshareholdermeeting.com/DINO2023SM and using the 16-digit control number on your proxy card.

Assuming a quorum is present, approval of the HF Sinclair Stock Issuance Proposal requires approval by a majority of the votes cast by HF Sinclair Stockholders entitled to vote on such proposal. The HF Sinclair Adjournment Proposal requires the approval by a majority in interest of the stockholders entitled to vote at the HF Sinclair Special Meeting, present in person or represented by proxy. Virtual attendance at the special meeting will constitute presence in person for the purpose of determining the presence of a quorum for the transaction of business at the HF Sinclair Special Meeting.

The parties to the Merger Agreement cannot complete the Merger unless the HF Sinclair Stock Issuance Proposal is approved at the HF Sinclair Special Meeting. Accordingly, your vote is very important regardless of the number of shares of HF Sinclair Common Stock you own.

The conflicts committee (the "HF Sinclair Conflicts Committee") of the board of directors of HF Sinclair (the "HF Sinclair Board") has unanimously (i) determined that the Merger Agreement and the Transactions, including the Merger and the HF Sinclair Stock Issuance, are advisable and in the best interests of HF Sinclair and the HF Sinclair Stockholders, (ii) approved the Merger Agreement and the Transactions, including the Merger and the

HF Sinclair Stock Issuance, on the terms and subject to the conditions set forth in the Merger Agreement,

1. recommended that the HF Sinclair Board approve the Merger Agreement and the Transactions, including the Merger and the HF Sinclair Stock Issuance, on the terms and subject to the conditions set forth in the Merger Agreement, and (iv) resolved and recommended that the HF Sinclair Board resolve, to (a) direct that the HF Sinclair Stock Issuance be submitted to a vote of the HF Sinclair Stockholders for approval at the HF Sinclair Special Meeting and (b) recommend approval of the HF Sinclair Stock Issuance by the HF Sinclair Stockholders at the HF Sinclair Special Meeting.

The HF Sinclair Board (acting, in part, based upon the recommendation of the HF Sinclair Conflicts Committee) has unanimously (i) determined that the Merger Agreement and the Transactions, including the Merger and the HF Sinclair Stock Issuance, are advisable and in the best interests of HF Sinclair and the HF Sinclair Stockholders, (ii) approved the Merger Agreement and the Transactions, including the Merger and the HF Sinclair Stock Issuance, on the terms and subject to the conditions set forth in the Merger Agreement,

1. directed that the HF Sinclair Stock Issuance be submitted to a vote of the HF Sinclair Stockholders for approval at the HF Sinclair Special Meeting and (iv) resolved to recommend approval of the HF Sinclair Stock Issuance by the HF Sinclair Stockholders at the HF Sinclair Special Meeting.

The HF Sinclair Board and HF Sinclair Conflicts Committee unanimously recommend that the HF Sinclair Stockholders vote "FOR" the HF Sinclair Stock Issuance Proposal. The HF Sinclair Board unanimously recommends that the HF Sinclair Stockholders vote "FOR" the HF Sinclair Adjournment Proposal. For more information regarding the recommendations of the HF Sinclair Board, see "Special Factors-Recommendationsof the HF Sinclair Conflicts Committee and the HF Sinclair Board and their Reasons for the Merger."

The HF Sinclair Stockholders should be aware that certain of the directors, executive officers and other affiliates of HF Sinclair may have interests in the Merger that are different from, or in addition to, the interests they may have as a HF Sinclair Stockholder. See "Special Factors-Interests of Certain Persons in the Merger."

Only the HF Sinclair Stockholders of record at the close of business on October 23, 2023 are entitled to notice of and to vote at the HF Sinclair Special Meeting. References to the HF Sinclair Special Meeting in this joint proxy statement/prospectus are to such virtual special meeting as the same may be adjourned or postponed from time to time.

TO PARTICIPATE IN THE VIRTUAL SPECIAL MEETING, A HF SINCLAIR STOCKHOLDER OF RECORD WILL NEED THE 16-DIGIT CONTROL NUMBER INCLUDED ON SUCH HOLDER'S PROXY CARD OR INSTRUCTIONS THAT ACCOMPANIED SUCH HOLDER'S PROXY MATERIALS. THE LIVE AUDIO WEBCAST OF THE HF SINCLAIR SPECIAL MEETING WILL BEGIN PROMPTLY ON NOVEMBER 28, 2023 AT 9:30 A.M., CENTRAL TIME, AT HTTPS://WWW.VIRTUALSHAREHOLDERMEETING.COM/DINO2023SM. THE HF SINCLAIR STOCKHOLDERS ARE ENCOURAGED TO ACCESS THE HF SINCLAIR SPECIAL MEETING PRIOR TO THE START TIME. ONLINE ACCESS AND CHECK-IN WILL BEGIN AT 9:15 A.M., CENTRAL TIME. TECHNICAL SUPPORT WILL BE AVAILABLE ON THE VIRTUAL MEETING PLATFORM BEGINNING AT 9:15 A.M., CENTRAL TIME ON NOVEMBER 28, 2023 THROUGH THE CONCLUSION OF THE HF SINCLAIR SPECIAL MEETING. IF YOU ENCOUNTER ANY DIFFICULTIES ACCESSING THE VIRTUAL MEETING DURING THE CHECK-IN OR MEETING TIME, PLEASE DIAL THE TECHNICAL ASSISTANCE NUMBERS SHOWN ON THE VIRTUAL MEETING PLATFORM. YOUR VOTE IS IMPORTANT. WHETHER OR NOT YOU EXPECT TO VIRTUALLY ATTEND THE HF SINCLAIR SPECIAL MEETING, PLEASE SUBMIT YOUR PROXY IN ONE OF THE FOLLOWING WAYS:

• If you hold your shares of HF Sinclair Common Stock in the name of a bank, broker or other nominee, you should follow the instructions provided by your bank, broker or other nominee when voting your shares of HF Sinclair Common Stock.

• If you hold your shares of HF Sinclair Common Stock in your own name, you may submit your proxy by:
• • using the toll-free telephone number shown on the proxy card and voting no later than 10:59 p.m., Central Time, on the date prior to the HF Sinclair Special Meeting;
  • using the Internet website shown on the proxy card and voting no later than 10:59 p.m., Central Time, on the date prior to the HF Sinclair Special Meeting; or
  • marking, signing, dating and promptly returning the enclosed proxy card in the postage-paid envelope. It requires no postage if mailed in the United States. To be counted at the HF Sinclair Special Meeting, the proxy card must be received no later than 10:59 p.m., Central Time, on the date prior to the HF Sinclair Special Meeting.

The enclosed joint proxy statement/prospectus provides a detailed description of the HF Sinclair Stock Issuance Proposal and the Merger Agreement. You are urged to read this joint proxy statement/prospectus, including any documents incorporated by reference, and the Annexes carefully and in their entirety. This joint proxy statement/ prospectus and the Notice of Virtual Special Meeting of Stockholders relating to the Merger and the HF Sinclair Stock Issuance Proposal will be available at https://www.proxyvote.com. If you have any questions concerning the Merger or the HF Sinclair Stock Issuance Proposal or this joint proxy statement/prospectus, would like additional copies or need help voting your shares of HF Sinclair Common Stock, please contact HF Sinclair's proxy solicitor:

MacKenzie Partners, Inc.

1407 Broadway

New York, New York 10018

Call [phone] /Toll-Free: [phone]

Email: [e-mail]

Sincerely,

Vaishali S. Bhatia

Executive Vice President, General Counsel and Secretary

HF Sinclair Corporation

Dallas, Texas

October 26, 2023

Holly Energy Partners, L.P.

2828 N. Harwood, Suite 1300

Dallas, Texas 75201

NOTICE OF VIRTUAL SPECIAL MEETING OF UNITHOLDERS

To the Unitholders of Holly Energy Partners, L.P.:

You are cordially invited to attend the virtual special meeting (as the same may be adjourned or postponed, the "HEP Special Meeting") of unitholders of Holly Energy Partners, L.P. ("HEP") which will be held exclusively via a live audio webcast on November 28, 2023 at 8:30 a.m., Central Time, at https://www.virtualshareholdermeeting.com/HEP2023SM, for the following purposes:

• to vote on a proposal to approve the Agreement and Plan of Merger (as the same may be amended or supplemented from time to time, the "Merger Agreement"), dated as of August 15, 2023, by and among HF Sinclair Corporation ("HF Sinclair"), Navajo Pipeline Co., L.P. ("HoldCo"), Holly Apple Holdings LLC ("Merger Sub"), HEP Logistics Holdings, L.P. ("HLH"), Holly Logistic Services, L.L.C. (the "General Partner") and HEP, and the transactions contemplated thereby, including the Merger (as defined below) (the "Merger Proposal"); and
• to vote on a proposal to approve the adjournment of the HEP Special Meeting to a later date or dates, if necessary or appropriate, to solicit additional proxies in the event there are not sufficient votes at the time of the HEP Special Meeting to approve the above proposal (the "HEP Adjournment Proposal").

The HEP Special Meeting will be held via a live audio webcast in a virtual meeting format at https://www.virtualshareholdermeeting.com/HEP2023SM. Holders of common units representing limited partner interests in HEP (the "HEP Common Units" and such holders, the "HEP Unitholders") will not be able to attend the HEP Special Meeting in-person. The accompanying joint proxy statement/prospectus includes instructions on how to access the virtual HEP Special Meeting and how to participate and vote from home or any remote location with Internet connectivity. You or your proxy holder will be able to virtually attend and vote at the virtual HEP Special Meeting by visiting https://www.virtualshareholdermeeting.com/HEP2023SM and using the 16-digit control number on your proxy card.

Upon the terms and subject to the conditions set forth in the Merger Agreement, upon consummation of the Merger (as defined below), Merger Sub will merge with and into HEP, with HEP surviving as an indirect wholly owned subsidiary of HF Sinclair (the "Merger"). Approval of the Merger Proposal requires the affirmative vote of holders of a majority of the outstanding HEP Common Units. In the absence of a quorum, approval of the HEP Adjournment Proposal requires the affirmative vote of HEP Unitholders representing a majority of the outstanding HEP Common Units entitled to vote and represented in person or by proxy at the HEP Special Meeting. If a quorum is present, approval of the HEP Adjournment proposal requires the affirmative vote of holders of a majority of the outstanding HEP Common Units. Virtual attendance at the special meeting will constitute presence in person for the purpose of determining the presence of a quorum for the transaction of business at the HF Sinclair Special Meeting.

Pursuant to the Merger Agreement, HF Sinclair has agreed that it will vote, or cause to be voted, all HEP Common Units then owned beneficially or of record by HF Sinclair or any of its subsidiaries in favor of the

Merger Proposal. HF Sinclair currently holds approximately 47% of the issued and outstanding HEP Common Units through its subsidiaries, along with the non-economic general partner interest and the special general partner interest.

The parties to the Merger Agreement cannot complete the Merger unless holders of a majority of the outstanding HEP Common Units approve the Merger Proposal. Accordingly, your vote is very important regardless of the number of HEP Common Units you own.

The conflicts committee (the "HEP Conflicts Committee") of the board of directors of the General Partner (the "GP Board") has unanimously and in good faith (i) determined that the Merger Agreement and the transactions contemplated thereby, including the Merger, are in the best interests of HEP, including the HEP Unitholders other than HF Sinclair, HoldCo, HLH, the General Partner and their respective Affiliates, including officers and directors of such entities and their Affiliates (the "HEP Unaffiliated Unitholders"), (ii) approved the Merger Agreement and the transactions contemplated thereby, including the Merger (the foregoing constituting "Special Approval" for all purposes of the Second Amended and Restated Agreement of Limited Partnership of HEP, dated as of October 31, 2017, as may be further amended, modified or supplemented from time to time, including Section 7.9(a) thereof) on the terms and subject to the conditions set forth in the Merger Agreement,

1. recommended that the GP Board approve the Merger Agreement and the transactions contemplated thereby, including the Merger, on the terms and subject to the conditions set forth in the Merger Agreement, and
2. resolved and recommended that the GP Board resolve to (a) direct that the Merger Agreement and the Merger be submitted to a vote of the HEP Unitholders for approval and (b) recommend approval of the Merger Agreement and the Merger by the HEP Unitholders at the HEP Special Meeting.

The GP Board (acting, in part, based upon the recommendation of the HEP Conflicts Committee) has unanimously and in good faith (i) determined that the Merger Agreement and the transactions contemplated thereby, including the Merger, are in the best interests of HEP, including the HEP Unaffiliated Unitholders,

1. approved the Merger Agreement and the transactions contemplated thereby, including the Merger, on the terms and subject to the conditions set forth in the Merger Agreement, (iii) directed that the Merger Agreement and the Merger be submitted to a vote of the HEP Unitholders for approval and (iv) resolved to recommend approval of the Merger Agreement and the Merger by the HEP Unitholders at the HEP Special Meeting.

Each of the HEP Conflicts Committee and the GP Board unanimously recommends that the HEP Unitholders vote "FOR" the Merger Proposal. The GP Board also recommends that the HEP Unitholders vote "FOR" the HEP Adjournment Proposal. For more information regarding the recommendations of the HEP Conflicts Committee and the GP Board, see "Special Factors-Recommendationsof the HEP Conflicts Committee and the GP Board and the Reasons for their Recommendations."

The HEP Unitholders should be aware that certain of the directors, executive officers and other affiliates of the General Partner and certain members of the HEP Conflicts Committee may have interests in the Merger that are different from, or in addition to, the interests they may have as a HEP Unitholder. See "Special Factors- Interests of Certain Persons in the Merger."

Only the HEP Unitholders of record at the close of business on October 23, 2023 are entitled to notice of and to vote at the HEP Special Meeting. References to the HEP Special Meeting in this joint proxy statement/prospectus are to such virtual special meeting as the same may be adjourned or postponed from time to time.

TO PARTICIPATE IN THE VIRTUAL SPECIAL MEETING, A HEP UNITHOLDER OF RECORD WILL NEED THE 16-DIGIT CONTROL NUMBER INCLUDED ON SUCH HOLDER'S PROXY CARD OR INSTRUCTIONS THAT ACCOMPANIED SUCH HOLDER'S PROXY MATERIALS. THE LIVE AUDIO WEBCAST OF THE HEP SPECIAL MEETING WILL BEGIN PROMPTLY ON NOVEMBER 28, 2023 AT 8:30 A.M., CENTRAL TIME, AT HTTPS://WWW.VIRTUALSHAREHOLDERMEETING.COM/ HEP2023SM. THE HEP UNITHOLDERS ARE ENCOURAGED TO ACCESS THE HEP SPECIAL MEETING PRIOR TO THE START TIME. ONLINE ACCESS AND CHECK-IN WILL BEGIN AT

8:15 A.M., CENTRAL TIME. TECHNICAL SUPPORT WILL BE AVAILABLE ON THE VIRTUAL

MEETING PLATFORM BEGINNING AT 8:15 A.M., CENTRAL TIME ON NOVEMBER 28, 2023 THROUGH THE CONCLUSION OF THE HEP SPECIAL MEETING. IF YOU ENCOUNTER ANY DIFFICULTIES ACCESSING THE VIRTUAL MEETING DURING THE CHECK-IN OR MEETING TIME, PLEASE DIAL THE TECHNICAL ASSISTANCE NUMBERS SHOWN ON THE VIRTUAL MEETING PLATFORM. YOUR VOTE IS IMPORTANT. WHETHER OR NOT YOU EXPECT TO VIRTUALLY ATTEND THE HEP SPECIAL MEETING, PLEASE SUBMIT YOUR PROXY IN ONE OF THE FOLLOWING WAYS:

• If you hold your HEP Common Units in the name of a bank, broker or other nominee, you should follow the instructions provided by your bank, broker or other nominee when voting your HEP Common Units.
• If you hold your HEP Common Units in your own name, you may submit your proxy by:
• • using the toll-free telephone number shown on the proxy card and voting no later than 10:59 p.m., Central Time, on the date prior to the HEP Special Meeting;
  • using the Internet website shown on the proxy card and voting no later than 10:59 p.m., Central Time, on the date prior to the HEP Special Meeting; or
  • marking, signing, dating and promptly returning the enclosed proxy card in the postage-paid envelope. It requires no postage if mailed in the United States. To be counted at the HEP Special Meeting, the proxy card must be received no later than 10:59 p.m., Central Time, on the date prior to the HEP Special Meeting.

The enclosed joint proxy statement/prospectus provides a detailed description of the Merger and the Merger Agreement. You are urged to read this joint proxy statement/prospectus, including any documents incorporated by reference, and the Annexes carefully and in their entirety. This joint proxy statement/prospectus and the Notice of Virtual Special Meeting of Unitholders relating to the Merger will be available at https://www.proxyvote.com. If you have any questions concerning the Merger or this joint proxy statement/prospectus, would like additional copies or need help voting your HEP Common Units, please contact HEP's proxy solicitor:

MacKenzie Partners, Inc.

1407 Broadway

New York, New York 10018

Call [phone] /Toll-Free: [phone]

Email: [e-mail]

Sincerely,

Vaishali S. Bhatia

Executive Vice President, General Counsel and Secretary Holly Logistic Services, L.L.C.

the general partner of HEP Logistics Holdings, L.P., which is the general partner of Holly Energy Partners, L.P.

IMPORTANT NOTE ABOUT THIS JOINT PROXY STATEMENT/PROSPECTUS

This joint proxy statement/prospectus, which forms part of a registration statement on Form S-4 filed with the SEC by HF Sinclair, constitutes a prospectus of HF Sinclair under Section 5 of the Securities Act with respect to the HF Sinclair Common Stock to be issued in connection with the Merger Agreement. This document also constitutes a proxy statement of HF Sinclair and of HEP under Section 14(a) of the Exchange Act and a notice of meeting with respect to the HF Sinclair Special Meeting and the HEP Special Meeting. This joint proxy statement/prospectus does not constitute an offer to exchange or sell, or a solicitation of offers to exchange or purchase or the solicitation of a proxy in any jurisdiction in which or from any person to whom it is unlawful to make any such offer or solicitation in such jurisdiction.

As permitted under the rules of the SEC, this joint proxy statement/prospectus incorporates by reference important business and financial information about HF Sinclair and HEP from other documents filed with the SEC that are not included in or delivered with this joint proxy statement/prospectus. See "Where You Can Find More Information" beginning on page 184. You can obtain any of the documents incorporated by reference into this document from HF Sinclair or HEP, as the case may be, or from the SEC's website athttp://www.sec.gov. This information is also available to you without charge upon your request in writing or by telephone from HF Sinclair or HEP at the following addresses and telephone numbers:

HF Sinclair Corporation	Holly Energy Partners, L.P.
Attention: Investor Relations	Attention: Investor Relations
2828 N. Harwood St., Suite 1300	2828 N. Harwood St., Suite 1300
Dallas, Texas 75201	Dallas, Texas 75201
Telephone: [phone]	Telephone: [phone]

Please note that copies of the documents provided to you will not include exhibits, unless the exhibits are specifically incorporated by reference into the documents or this joint proxy statement/prospectus.

You may obtain certain of these documents at HF Sinclair's website at http://www.hfsinclair.comand HEP's website at http://www.hollyenergy.com. Information contained on HF Sinclair's and HEP's websites is expressly not incorporated by reference into this joint proxy statement/prospectus.

In order to receive timely delivery of requested documents in advance of the HF Sinclair Special Meeting and HEP Special Meeting, your request should be received no later than five business days before the date of each respective Special Meeting, which means your request should be received no later than November 20, 2023. If you request any documents, HF Sinclair or HEP, as applicable, will mail them to you by first class mail, or another equally prompt means, after receipt of your request.

In "Questions and Answers" and in the "Summary Term Sheet" below, selected information from this joint proxy statement/prospectus is highlighted, but not all of the information that may be important to you is included. To better understand the Merger Agreement, the Merger and the HF Sinclair Stock Issuance, and for a more complete description of its legal terms, you should carefully read this entire joint proxy statement/prospectus, including the section entitled "Risk Factors" beginning on page 22 of this joint proxy statement/prospectus and the Merger Agreement, a copy of which is attached hereto as Annex A, as well as the documents that are incorporated by reference into this joint proxy statement/prospectus. See "Where You Can Find More Information."

HF Sinclair and HEP have not authorized anyone to give any information or make any representation about the Merger, HF Sinclair or HEP that is different from, or in addition to, that contained in this joint proxy statement/ prospectus or in any of the materials that have been incorporated by reference into this joint proxy statement/ prospectus. Therefore, if anyone distributes this type of information, you should not rely on it. If you are in a jurisdiction where offers to exchange or sell, or solicitations of offers to exchange or purchase, the securities offered by this joint proxy statement/prospectus or the solicitation of proxies are unlawful, or you are a person to whom it is unlawful to direct these types of activities, then the offer presented in this joint proxy statement/