O'Reilly Automotive (ORLY)

Supplemental Indenture

On December 31, 2008, O’Reilly Automotive, Inc. entered into the Fourth Supplemental Indenture (the “Fourth Supplemental Indenture”) with respect to the $100 million principal amount of 6¾% Exchangeable Senior Notes due 2025, originally issued by CSK Auto Corporation (“CSK”) pursuant to an Indenture, dated as of December 19, 2005, as amended and supplemented by the First Supplemental Indenture dated as of December 30, 2005, the Second Supplemental Indenture dated as of July 27, 2006, and the Third Supplemental Indenture dated as of July 11, 2008, by and between CSK, CSK Auto, Inc. and The Bank of New York Mellon Trust Company, N.A., as trustee, in order to correct the definition of Exchange Rate.  The Fourth Supplemental Indenture is effective as of July 11, 2008.

The foregoing summary of the material terms of the Fourth Supplemental Indenture is not complete and is qualified in its entirety by the complete terms and conditions of the Fourth Supplemental Indenture, which is filed as Exhibit 10.1 to this Current Report on Form 8-K and is incorporated herein by reference.

THIRD SUPPLEMENTAL INDENTURE

This THIRD SUPPLEMENTAL INDENTURE (the “Third Supplemental Indenture”) is dated as of July 11, 2008, between O’Reilly Automotive, Inc., a Missouri corporation (“O’Reilly”), CSK Auto, Inc., an Arizona corporation (the “Company”), the Guarantors named herein and The Bank of New York Mellon Trust Company, N.A., as trustee (the “Trustee”).

WHEREAS, the Company, CSK Auto Corporation, a Delaware Corporation (“CSK”), and the Trustee are parties to an Indenture, dated as of December 19, 2005, as amended and supplemented by the First Supplemental Indenture (the “First Supplemental Indenture”) dated as of December 30, 2005 and the Second Supplemental Indenture, dated as of July 27, 2006 (the “Second Supplemental Indenture”) (as amended and supplemented by the First Supplemental Indenture and the Second Supplemental Indenture, the “Indenture”), pursuant to which the Company issued its 45/8% (as increased to 6 ³/ 4% by the Second Supplemental Indenture) Exchangeable Senior Notes due 2025 (the “Notes”);

WHEREAS, on April 1, 2008, CSK entered into an Agreement and Plan of Merger by and among O’Reilly and OC Acquisition Company, a Delaware corporation and an indirect wholly-owned Subsidiary of O’Reilly (“Merger Sub”) (the “Merger Agreement”), pursuant to which, among other things, Merger Sub will merge with and into CSK (the “Merger”);

WHEREAS, Section 11.01 of the Indenture provides that CSK shall not merge or enter into certain other transactions unless certain requirements specified therein are satisfied;

WHEREAS, Section 14.06 provides that if a merger or certain other transactions involving CSK occur, as a result of which holders of Common Stock of CSK shall be entitled to receive cash, securities or other property with respect to or in exchange for such Common Stock, then CSK and the Company shall enter into a supplemental indenture providing that each Note shall be exchangeable into the kind and amount of cash, securities or other property receivable upon such transaction by holders of Common Stock of CSK;

WHEREAS, Section 10.01(b) of the Indenture provides that the Company, CSK, the Subsidiary Guarantors and the Trustee may enter into indentures supplemental thereto to modify the Indenture in accordance with Section 14.06;

WHEREAS, O’Reilly wishes to become a guarantor (in such capacity, the “Guarantor”), on a subordinated basis, of the obligations of the Company under the Indenture and the Notes and enter into an indenture supplemental to the Indenture providing for such guarantee (the “Subordinated Guarantee”);

WHEREAS, Section 10.01(d) of the Indenture provides that the Company, CSK, the Subsidiary Guarantors and the Trustee may enter into indentures supplemental thereto to add guarantees or guarantors with respect to the Notes;

WHEREAS, the execution and delivery of this instrument has been duly authorized and all conditions and requirements necessary to make this instrument a valid and binding agreement have been duly performed and complied with; and

WHEREAS, this Third Supplemental Indenture is being executed and delivered concurrently with the effectiveness of the Merger.

NOW, THEREFORE, in consideration of the premises set forth herein and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, it is mutually covenanted and agreed, for the equal and proportionate benefit of all Holders, as follows:

FIRST SUPPLEMENTAL INDENTURE

FIRST SUPPLEMENTAL INDENTURE (this “Supplemental Indenture”), dated as of December 30, 2005, among, MDAS, Inc., a Delaware corporation (“MDAS”), Murray’s Discount Auto Stores, Inc., a Michigan corporation (“Murray’s Stores,” together with MDAS, the “New Guarantors” and each a “New Guarantor”), CSK AUTO, INC., an Arizona corporation (the “Company”), CSK AUTO CORPORATION, a Delaware corporation and the parent of the Company (the “Issuer”), and THE BANK OF NEW YORK TRUST COMPANY, N.A., a national banking association, as trustee under the indenture referred to below (the “Trustee”).

WITNESSETH:

WHEREAS the Company, the Issuer and the existing Subsidiary Guarantors have heretofore executed and delivered to the Trustee an Indenture (as amended, supplemented or otherwise modified, the “Indenture”) dated as of December 19, 2005, providing for the issuance of the Company’s 4 ⁵/8% Senior Exchangeable Notes due 2025 (the “Notes”), initially in the aggregate principal amount of $85,000,000 (or up to $100,000,000 if the Initial Purchasers exercise their over-allotment option set forth in the Purchase Agreement in full), and Additional Notes as provided in the Indenture;

WHEREAS Section 4.10 of the Indenture provides that under certain circumstances the Company is required to cause each New Guarantor to execute and deliver to the Trustee a supplemental indenture pursuant to which such New Guarantor shall unconditionally guarantee all the Company’s obligations under the Notes and the Indenture pursuant to a Guarantee on the terms and conditions set forth herein and in the Indenture; and

WHEREAS pursuant to Section 10.01 of the Indenture, the Trustee, the Company, the Issuer and the existing Subsidiary Guarantors are 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, each New Guarantor, the Company, the Issuer and the Trustee mutually covenant and agree for the equal and ratable benefit of the holders of the Notes as follows:

1. Defined Terms. As used in this Supplemental Indenture, terms defined in the Indenture or in the preamble or recital hereto are used herein as therein defined. The words “herein,” “hereof” and “hereby” and other words of similar import used in this Supplemental Indenture refer to this Supplemental Indenture as a whole and not to any particular section hereof.

2. Agreement to Guarantee. Each New Guarantor hereby agrees, jointly and severally with the Issuer and all existing Subsidiary Guarantors, to unconditionally guarantee the Company’s obligations under the Notes and the Indenture on the terms and subject to the conditions set forth in Article 15 of the Indenture and to be bound by all other applicable provisions of the Indenture and the Notes and to perform all of the obligations and agreements of a Subsidiary Guarantor under the Indenture.

3. Notices. All notices or other communications to each New Guarantor shall be given as provided in Section 16.03 of the Indenture.

4. Ratification of Indenture; Supplemental Indentures Part of Indenture. Except as expressly amended hereby, the Indenture is in all respects ratified and confirmed and all the terms, conditions and provisions thereof shall remain in full force and effect. This Supplemental Indenture shall form a part of the Indenture for all purposes, and every holder of Notes heretofore or hereafter authenticated and delivered shall be bound hereby.

5. Governing Law. THIS SUPPLEMENTAL INDENTURE SHALL BE GOVERNED BY, AND CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK

6. Trustee Makes No Representation. The Trustee makes no representation as to the validity or sufficiency of this Supplemental Indenture.

7. Execution in Counterparts. This Supplemental Indenture may be executed in any number of counterparts, each of which shall be an original, but such counterparts shall together constitute but one and the same instrument.

8. Effect of Headings. The titles and headings of the Sections of this Supplemental Indenture have been inserted for convenience of reference only, and are not to be considered a part hereof, and shall in no way modify or restrict any of the terms or provisions hereof.

2

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

3

4

SECOND SUPPLEMENTAL INDENTURE

SECOND SUPPLEMENTAL INDENTURE dated as of July 27, 2006 (this “Supplemental Indenture” ) among CSK Auto, Inc., an Arizona corporation (the “Company”), CSK Auto Corporation, a Delaware corporation and the parent of the Company (the “Issuer”), CSKAUTO.COM, Inc., a Delaware corporation (the “Subsidiary Guarantor”), and The Bank of New York Trust Company, N.A., a national banking association, as trustee under the indenture referred to below (the “Trustee”).

Supplemental Indenture

On July 11, 2008, O’Reilly agreed to become a guarantor, on a subordinated basis, of the $100 million principal amount of 6 ³/4% Exchangeable Senior Notes due 2025 (the “Notes”) originally issued by CSK pursuant to an Indenture (the “Original Indenture”), dated as of December 19, 2005, as amended and supplemented by the First Supplemental Indenture (the “First Supplemental Indenture”) dated as of December 30, 2005 and the Second Supplemental Indenture, dated as of July 27, 2006 (the “Second Supplemental Indenture”) by and between CSK, CSK Auto, Inc. and The Bank of New York Mellon Trust Company, N.A., as trustee.

2

On July 11, 2008, O’Reilly executed the Third Supplemental Indenture (the “Third Supplemental Indenture” and together with the Original Indenture, the First Supplemental Indenture and the Second Supplemental Indenture, the “Indenture”), in which it agreed to unconditionally guarantee, on a subordinated basis, the payment of interest and principal on the Notes. The Third Supplemental Indenture also provides that each Note is exchangeable into the kind and amount of cash, securities or other property (and in the same proportion) receivable upon the merger of an indirect wholly owned subsidiary of O’Reilly with and into CSK by a holder of a number of shares of CSK common stock issuable upon exchange of the Notes immediately prior to such merger.

The foregoing summary of the material terms of the Indenture is not complete and is qualified in its entirety by the complete terms and conditions of the Indenture, which is filed as Exhibits 10.2, 10.3, 10.4 and 10.5 to this Current Report on Form 8-K and is incorporated herein by reference.