UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the

Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): May 13 26, 2011

FRONTIER OIL CORPORATION

(Exact name of registrant as specified in its charter)

WYOMING	1-7627	174-~~7627~~1895085	~~74-1895085~~
(State or other jurisdiction of incorporation or organization)	(Commission File Number)	(~~Commission~~I.R.S. ~~File~~Employer ~~Number~~Identification No.)	~~(I.R.S. Employer Identification No.)~~
10000 Memorial Drive, Suite 600 Houston, Texas			77024
(Address of principal executive offices)			(Zip Code)

10000 Memorial Drive, Suite 600 Houston, Texas	77024
(Address of principal executive offices)	(Zip Code)

Registrant’s telephone number, including area code: (713) 688-9600

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

xþ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

¨o Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

¨o Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.14d-2(b))

¨o Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

ITEM 1.01 Entry Into a Definitive Material Agreement

On May 26, 2011, Frontier Oil Corporation (the “Company”) and Wells Fargo Bank, N.A., as trustee, under each of the indentures dated September 17, 2008 and November 22, 2010, each as supplemented, by and among the Company, the guarantors named therein and the trustee, relating to the Company’s 8.5% Senior Notes due 2016 and the Company’s 6.875% Senior Notes due 2018, entered into supplemental indentures to amend certain terms of the indentures. The Company received the requisite consents to execute the supplemental indentures on May 26, 2011, pursuant to its previously announced consent solicitations. The supplemental indentures effect the proposed amendments to the indentures as described in the Company’s Consent Solicitation Statement, dated as of May 13, 2011. The amendments to the indentures designate each of Holly Energy Partners, L.P., a publicly traded limited partnership in which Holly Corporation has a 34% ownership interest and indirectly owns the general partner (“HEP”), and HEP’s subsidiaries as an “Unrestricted Subsidiary” under the indentures, except HEP and its subsidiaries and certain affiliates from certain covenant restrictions contained in the indentures and make certain other amendments with respect to the transactions with affiliates and additional guarantor covenants. The amendments will become effective only upon consummation of the proposed merger of North Acquisition, Inc., a subsidiary of Holly Corporation, into the Company in connection with the previously announced merger agreement among those parties.

The foregoing description of the supplemental indentures is qualified by the terms of the supplemental indentures, which are attached hereto as Exhibits 4.1 and 4.2 and incorporated herein by reference.

ITEM 8.01. Other Events.

On May 13 26, 2011, Frontier Oil Corporation ~~(“Frontier”)~~ issued a ~~weekly~~press ~~communiqué~~release toannouncing ~~its employees in connection with~~ the ~~Agreement~~expiration ~~and Plan~~ of ~~Merger,~~its byconsent ~~and~~solicitations ~~among~~from ~~Frontier,~~the ~~Holly~~holders ~~Corporation~~of ~~(“Holly”)~~its ~~and~~8.5% ~~North Acquisition,~~Senior ~~Inc.~~Notes ~~(“Merger~~due ~~Sub”),~~2016 ~~pursuant~~in toaggregate ~~which~~principal ~~Merger~~amount ~~Sub~~outstanding ~~will~~of ~~merge~~$200 ~~with~~million and ~~into~~its ~~Frontier,~~6.875% ~~with~~Senior ~~Frontier~~Notes ~~surviving~~due ~~the~~2018 ~~merger~~in asaggregate aprincipal ~~wholly~~amount ~~owned~~outstanding ~~subsidiary~~ of ~~Holly~~$150 ~~(the~~million ~~“Merger”).~~to ~~Among~~effect ~~other~~amendments ~~things,~~to ~~this~~the ~~communiqué announced~~indentures ~~that~~governing ~~Frontier anticipates a July 1, 2011 closing of~~ the ~~Merger~~notes.

A copy of this ~~communiqué~~press asrelease ~~sent to employees~~ is set forth in Exhibit 99.1 hereto and incorporated herein by reference.

Important Information for Investors and Shareholders

This communication does not constitute an offer to sell or the solicitation of an offer to buy any securities or a solicitation of any vote or approval. The issuance of Holly Corporation (“Holly”) common stock in connection with the proposed merger will be submitted to Holly’s shareholders for their consideration, and the proposed merger will be submitted to shareholders of Frontier Oil Corporation (“Frontier”) for their consideration. Holly filed with the Securities and Exchange Commission (“SEC”) a registration statement on Form S-4 that included a joint proxy statement to be used by Holly and Frontier to solicit the required approval of their shareholders in connection with the proposed merger and constituted a prospectus of Holly. Holly and Frontier may also file other documents with the SEC concerning the proposed merger. INVESTORS AND SECURITY HOLDERS OF HOLLY AND FRONTIER ARE URGED TO READ THE JOINT PROXY STATEMENT/PROSPECTUS REGARDING THE PROPOSED MERGER AND OTHER RELEVANT DOCUMENTS FILED WITH THE SEC CAREFULLY AND IN THEIR ENTIRETY WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED MERGER. Investors and security holders may obtain a free copy of the joint proxy statement/prospectus and other documents containing important information about Holly and Frontier through the website maintained by the SEC at www.sec.gov. Copies of the documents filed with the SEC by Holly will be available free of charge on Holly’s website at www.hollycorp.com under the tab “Investors” or by contacting Holly’s Investor Relations Department at (214) 871-3555. Copies of documents filed with the SEC by Frontier will be available free of charge on Frontier’s website at www.frontieroil.com under the tab “Investor Relations” and then under the tab “SEC Filings” or by contacting Frontier’s Investor Relations Department at (713) 688-9600.

Holly, Frontier and certain of their respective directors and executive officers may be deemed to be participants in the solicitation of proxies from the shareholders of Holly and shareholders of Frontier in connection with the proposed transaction. Information about the directors and executive officers of Holly is set forth in its proxy statement for its 2011 annual meeting of shareholders, which was filed with the SEC on March 31, 2011. Information about the directors and executive officers of Frontier is set forth in its proxy statement for its 2011 annual meeting of shareholders, which was filed with the SEC on March 21, 2011. These documents can be obtained free of charge from the sources indicated above. Other information regarding the participants in the proxy solicitation and a description of their direct and indirect interests, by security holdings or otherwise, are contained in the joint proxy statement/prospectus and other relevant materials to be filed with the SEC.

Cautionary Statement Regarding Forward-Looking Statements

This communication contains “forward-looking” statements within the meaning of Section 27A of the Securities Act of 1933, and Section 21E of the Securities Exchange Act of 1934. These include statements regarding the effects of the proposed merger and statements preceded by, followed by or that otherwise include the words “believes,” “expects,” “anticipates,” “intends,” “estimates,” or similar expressions. Forward looking statements relating to expectations about future results or events are based upon information available to Holly and Frontier as of today’s date, and are not guarantees of the future performance of Holly, Frontier or the combined company, and actual results may vary materially from the results and expectations discussed. For instance, although Holly and Frontier have signed an agreement for a subsidiary of Holly to merge with and into Frontier, there is no assurance that they will complete the proposed merger by a specified date or at all. The merger agreement will terminate if the companies do not receive the necessary approval of Holly’s shareholders or Frontier’s shareholders or government approvals or if either Holly or Frontier fails to satisfy conditions to closing. Additional risks and uncertainties related to the proposed merger include, but are not limited to, the successful integration of Holly’s and Frontier’s business and the combined company’s ability to compete in the highly competitive refining and marketing industry. The revenues, earnings and business prospects of Holly, Frontier and the combined company and their ability to achieve planned business objectives will be subject to a number of risks and uncertainties. These risks and uncertainties include, among other things, risks and uncertainties with respect to the actions of actual or potential competitive suppliers of refined petroleum products in Holly’s, Frontier’s and the combined company’s markets; the demand for and supply of crude oil and refined products; the spread between market prices for refined products and market prices for crude oil; the possibility of constraints on the transportation of refined products; the possibility of inefficiencies, curtailments or shutdowns in refinery operations or pipelines; effects of governmental and environmental regulations and policies; the availability and cost of financing; the effectiveness of capital investments and marketing strategies; efficiency in carrying out construction projects; the ability to acquire refined product operations or pipeline and terminal operations on acceptable terms and to integrate any existing or future acquired operations; the possibility of terrorist attacks and the consequences of any such attacks; and general economic conditions.

Holly and Frontier caution that the foregoing list of risks and uncertainties is not exclusive. Additional information concerning these and other risks is contained in Holly’s and Frontier’s most recently filed Annual Reports on Form 10-K, subsequent Quarterly Reports on Form 10-Q, recent Current Reports on Form 8-K and other SEC filings. All subsequent written and oral forward-looking statements concerning Holly, Frontier, the proposed merger or other matters and attributable to Holly or Frontier or any person acting on their behalf are expressly qualified in their entirety by the cautionary statements above. Neither Holly nor Frontier undertake any obligation to publicly update any of these forward-looking statements to reflect events or circumstances that may arise after the date hereof.

ITEM 9.01. Financial Statements and Exhibits.

ExhibitNumber		Description
Exhibit Number		Description
99.1		Communiqué by Frontier Oil Corporation, issued to employees on May 13, 2011.
4.1		Second Supplemental Indenture, dated as of May 26, 2011, among Frontier Oil Corporation, the guarantors party thereto and Wells Fargo Bank, N.A., as trustee (relating to the 8.5% Senior Notes due 2016)
4.2		Second Supplemental Indenture, dated as of May 26, 2011, among Frontier Oil Corporation, the guarantors party thereto and Wells Fargo Bank, N.A., as trustee (relating to the 6.875% Senior Notes due 2018)
99.1		Press release, dated May 26, 2011, issued by Frontier Oil Corporation.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

	FRONTIER OIL CORPORATION
	By: /s/ Doug S. Aron Name: Doug S. Aron Title: Executive Vice President and Chief Financial Officer

Date: May 13 27, 2011

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