SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                  Schedule 13D

                    Under the Securities Exchange Act of 1934

                                 Amendment No. 2


                                  Premcor Inc.
          ------------------------------------------------------------
                                (Name of Issuer)


                                  Common Stock
          ------------------------------------------------------------
                         (Title of Class of Securities)


                                   74045Q 10 4
          ------------------------------------------------------------
                                 (CUSIP Number)


                            Donald P. de Brier, Esq.
                        Occidental Petroleum Corporation
                            10889 Wilshire Boulevard
                          Los Angeles, California 90024
                                 (310) 208-8800
          ------------------------------------------------------------
            (Name, Address and Telephone Number of Person Authorized
                     to Receive Notices and Communications)


                                  May 26, 2005
          ------------------------------------------------------------
             (Date of Event Which Requires Filing of this Statement)


If the filing person has previously filed a statement on Schedule 13G to report
the acquisition which is the subject of this Schedule 13D, and is filing this
schedule because of Rule 13d-l(e), 13d-1(f) or 13d-1(g), check the following box
[ ]


                               Page 1 of 11 Pages

CUSIP No. 74045Q 10 4 ----------- (1) Names of reporting persons. Occidental Petroleum Corporation I.R.S. Identification Nos. of above persons (entities only). 95-4035997 (2) Check the appropriate box if a member of a group (a) (see instructions) (b) (3) SEC use only. (4) Source of funds (see instructions). OO (5) Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e). (6) Citizenship or place of organization. Delaware Number of shares beneficially owned by each reporting person with: (7) Sole voting power. 0 (8) Shared voting power. 9,034,646 (9) Sole dispositive power. 0 (10) Shared dispositive power. 9,034,646 (11) Aggregate amount beneficially owned by each reporting person 9,034,646 (12) Check if the aggregate amount in Row (11) excludes certain shares (see instructions). (13) Percent of class represented by amount in Row (11). 10.13% (14) Type of reporting person (see instructions). CO Page 2 of 11 Pages

CUSIP No. 74045Q 10 4 ----------- (1) Names of reporting persons. Occidental C.O.B. Partners I.R.S. Identification Nos. of above persons (entities only). 73-1484588 (2) Check the appropriate box if a member of a group (a) (see instructions) (b) (3) SEC use only. (4) Source of funds (see instructions). OO (5) Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e). (6) Citizenship or place of organization. Delaware Number of shares beneficially owned by each reporting person with: (7) Sole voting power. 0 (8) Shared voting power. 9,034,646 (9) Sole dispositive power. 0 (10) Shared dispositive power. 9,034,646 (11) Aggregate amount beneficially owned by each reporting person 9,034,646 (12) Check if the aggregate amount in Row (11) excludes certain shares (see instructions). (13) Percent of class represented by amount in Row (11). 10.13% (14) Type of reporting person (see instructions). PN Page 3 of 11 Pages

CUSIP No. 74045Q 10 4 ----------- (1) Names of reporting persons. Placid Oil Company I.R.S. Identification Nos. of above persons (entities only). 72-0395174 (2) Check the appropriate box if a member of a group (a) (see instructions) (b) (3) SEC use only. (4) Source of funds (see instructions). OO (5) Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e). (6) Citizenship or place of organization. Delaware Number of shares beneficially owned by each reporting person with: (7) Sole voting power. 0 (8) Shared voting power. 9,034,646 (9) Sole dispositive power. 0 (10) Shared dispositive power. 9,034,646 (11) Aggregate amount beneficially owned by each reporting person 9,034,646 (12) Check if the aggregate amount in Row (11) excludes certain shares (see instructions). (13) Percent of class represented by amount in Row (11). 10.13% (14) Type of reporting person (see instructions). CO Page 4 of 11 Pages

CUSIP No. 74045Q 10 4 ----------- (1) Names of reporting persons. OXY USA Inc. I.R.S. Identification Nos. of above persons (entities only). 73-1166880 (2) Check the appropriate box if a member of a group (a) (see instructions) (b) (3) SEC use only. (4) Source of funds (see instructions). OO (5) Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e). (6) Citizenship or place of organization. Delaware Number of shares beneficially owned by each reporting person with: (7) Sole voting power. 0 (8) Shared voting power. 9,034,6467 (9) Sole dispositive power. 0 (10) Shared dispositive power. 9,034,646 (11) Aggregate amount beneficially owned by each reporting person 9,034,646 (12) Check if the aggregate amount in Row (11) excludes certain shares (see instructions). (13) Percent of class represented by amount in Row (11). 10.13% (14) Type of reporting person (see instructions). CO Page 5 of 18 Pages

CUSIP No. 74045Q 10 4 ----------- (1) Names of reporting persons. Occidental Oil and Gas Holding Corporation I.R.S. Identification Nos. of above persons (entities only). 95-2864974 (2) Check the appropriate box if a member of a group (a) (see instructions) (b) (3) SEC use only. (4) Source of funds (see instructions). OO (5) Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e). (6) Citizenship or place of organization. California Number of shares beneficially owned by each reporting person with: (7) Sole voting power. 0 (8) Shared voting power. 9,034,646 (9) Sole dispositive power. 0 (10) Shared dispositive power. 9,034,646 (11) Aggregate amount beneficially owned by each reporting person 9,034,646 (12) Check if the aggregate amount in Row (11) excludes certain shares (see instructions). (13) Percent of class represented by amount in Row (11). 10.13% (14) Type of reporting person (see instructions). CO Page 6 of 11 Pages

CUSIP No. 74045Q 10 4 ----------- (1) Names of reporting persons. Occidental Petroleum Investment Co. I.R.S. Identification Nos. of above persons (entities only). 95-2584267 (2) Check the appropriate box if a member of a group (a) (see instructions) (b) (3) SEC use only. (4) Source of funds (see instructions). OO (5) Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e). (6) Citizenship or place of organization. California Number of shares beneficially owned by each reporting person with: (7) Sole voting power. 0 (8) Shared voting power. 9,034,646 (9) Sole dispositive power. 0 (10) Shared dispositive power. 9,034,646 (11) Aggregate amount beneficially owned by each reporting person 9,034,646 (12) Check if the aggregate amount in Row (11) excludes certain shares (see instructions). (13) Percent of class represented by amount in Row (11). 10.13% (14) Type of reporting person (see instructions). CO Page 7 of 11 Pages

ITEM 4. PURPOSE OF THE TRANSACTION. Item 4 of the previously filed Schedule 13D is amended as follows: Occidental currently intends to dispose of the shares of Premcor beneficially owned by it either from time to time in one or more open market transactions or pursuant to the agreement between Valero Energy Corp. ("Valero") and Premcor, providing for the purchase by Valero of all of the outstanding shares of Premcor. Occidental's determination as to when and if Occidental will dispose of the Premcor shares will be based upon a variety of factors, including, without limitation, the price of the Premcor shares in the market and other market conditions. Except as described in this Item 4, Occidental currently has no plans that relate to or would result in or any of the actions listed in clauses (a) through (j) of Item 4 of Schedule 13D. ITEM 5. INTEREST IN SECURITIES OF THE ISSUER. (a) Occidental: aggregate number of shares held: 9,034,646 ----------- percentage of class: 10.13% Oxy Partners: aggregate number of shares held: 9,034,646 ------------- percentage of class: 10.13% Placid: aggregate number of shares held: 9,034,646 ------- percentage of class: 10.13% OXY USA: aggregate number of shares held: 9,034,646 -------- percentage of class: 10.13% OOGHC: aggregate number of shares held: 9,034,646 ------ percentage of class: 10.13% OPIC: aggregate number of shares held: 9,034,646 ----- percentage of class: 10.13% (b) Occidental: sole power to vote or direct the vote: 0 ----------- shared power to vote or direct the vote: 9,034,646 sole power to dispose or direct the disposition: 0 shared power to dispose or direct the disposition: 9,034,646 Oxy Partners: sole power to vote or direct the vote: 0 ------------- shared power to vote or direct the vote: 9,034,646 sole power to dispose or direct the disposition: 9,034,646 Page 8 of 11 Pages

Placid: sole power to vote or direct the vote: 0 ------- shared power to vote or direct the vote: 9,034,646 sole power to dispose or direct the disposition: 0 shared power to dispose or direct the disposition: 9,034,646 OXY USA: sole power to vote or direct the vote: 0 -------- shared power to vote or direct the vote: 9,034,646 sole power to dispose or direct the disposition: 0 shared power to dispose or direct the disposition: 9,034,646 OOGHC: sole power to vote or direct the vote: 0 ------ shared power to vote or direct the vote: 9,034,646 sole power to dispose or direct the disposition: 0 shared power to dispose or direct the disposition: 9,034,646 OPIC: sole power to vote or direct the vote: 0 ----- shared power to vote or direct the vote: 9,034,646 sole power to dispose or direct the disposition: 0 shared power to dispose or direct the disposition: 9,034,646 (c) On May 26, 2005, Occidental and the other members of the group filing this Amendment entered into an Assignment and Contribution Agreement, transferring ownership of the shares held directly by Occidental to Occidental C.O.B. Partners. ITEM 7. MATERIAL TO BE FILED AS EXHIBITS. Exhibit 1 Agreement Pursuant to Rule 13d-1(k) Exhibit 2 Second Amended and Restated Stockholders' Agreement, dated as of November 3, 1997, between Oxy Partners and Premcor, Inc.* Exhibit 3 Form of Warrant Exercise and Share Exchange Agreement, dated as of April 26, 2002 (the "Exercise and Exchange Agreement"), by and among Occidental Oxy Partners, Blackstone Capital Partners III Merchant Banking Fund L.P., a Delaware limited partnership, Blackstone Offshore Capital Partners III L.P., a Delaware limited partnership, Blackstone Family Investment Partnership III L.P., a Delaware limited partnership, Premcor and Sabine* Exhibit 4 Commitment Letter, dated November 25, 2002* Exhibit 5 Assignment and Contribution Agreement, dated May 26, 2005 - ---------- *Previously filed. Page 9 of 11 Pages

SIGNATURE After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct. May 31, 2005 OCCIDENTAL PETROLEUM CORPORATION By: /s/ J. R. HAVERT ----------------------------------------------- Name: J. R. Havert Title: Vice President and Treasurer OCCIDENTAL C.O.B. PARTNERS by OXY USA Inc., its managing partner By: /s/ J. R. HAVERT ----------------------------------------------- Name: J. R. Havert Title: Vice President and Treasurer PLACID OIL COMPANY By: /s/ J. R. HAVERT ----------------------------------------------- Name: J. R. Havert Title: Vice President and Treasurer OXY USA INC. By: /s/ J. R. HAVERT ----------------------------------------------- Name: J. R. Havert Title: Vice President and Treasurer OCCIDENTAL OIL AND GAS HOLDING CORPORATION By: /s/ J. R. HAVERT ----------------------------------------------- Name: J. R. Havert Title: Vice President and Treasurer Page 10 of 11 Pages

OCCIDENTAL PETROLEUM INVESTMENT CO. By: /s/ J. R. HAVERT ----------------------------------------------- Name: J. R. Havert Title: Vice President and Treasurer Page 11 of 11 Pages

                                                                       EXHIBIT 1

                                    AGREEMENT

     Pursuant to Rule 13d-1(k) promulgated under the Securities Exchange Act of
1934, as amended, the undersigned agree that the Amendment No. 1 to Schedule 13D
to which this Agreement is attached as Exhibit 1 is filed on behalf of each of
us. This Agreement may be executed in two or more counterparts, each of which
shall be deemed an original, but all of which together shall constitute one and
the same agreement.


May 31, 2005                  OCCIDENTAL PETROLEUM CORPORATION


                              By: /s/ J. R. HAVERT
                                 -----------------------------------------------
                                 Name:  J. R. Havert
                                 Title: Vice President and Treasurer


                              OCCIDENTAL C.O.B. PARTNERS
                              by OXY USA Inc., its managing partner


                              By: /s/ J. R. HAVERT
                                 -----------------------------------------------
                                 Name:  J. R. Havert
                                 Title: Vice President and Treasurer


                              PLACID OIL COMPANY


                              By: /s/ J. R. HAVERT
                                 -----------------------------------------------
                                 Name:  J. R. Havert
                                 Title: Vice President and Treasurer


                              OXY USA INC.


                              By: /s/ J. R. HAVERT
                                 -----------------------------------------------
                                 Name:  J. R. Havert
                                 Title: Vice President and Treasurer


                                Page 1 of 2 Pages

OCCIDENTAL OIL AND GAS HOLDING CORPORATION By: /s/ J. R. HAVERT ----------------------------------------------- Name: J. R. Havert Title: Vice President and Treasurer OCCIDENTAL PETROLEUM INVESTMENT CO. By: /s/ J. R. HAVERT ----------------------------------------------- Name: J. R. Havert Title: Vice President and Treasurer Page 2 of 2 Pages


                      ASSIGNMENT AND CONTRIBUTION AGREEMENT


     This Assignment and Contribution Agreement ("Agreement") is made effective
as of May 27, 2005, by and among the signatories hereto.

                                    RECITALS

     WHEREAS, Occidental Petroleum Corporation, a Delaware corporation ("OPC"),
presently owns 1,908,209 shares of the capital stock of Premcor Inc., a Delaware
corporation ("PREMCOR"), and said ownership interest being herein referred to as
the "Ownership Interest"; and

     WHEREAS, OPC desires to contribute the value of the Ownership Interest in
PREMCOR to Occidental Petroleum Investment Co., a California corporation
("OPIC"), as a contribution to capital; and

     WHEREAS, OPIC desires to contribute the value of the Ownership Interest in
PREMCOR to Occidental Oil and Gas Holding Corporation, a California corporation
("OOGHC"), as a contribution to capital; and

     WHEREAS, OOGHC desires to contribute an 80% portion of the value of the
Ownership Interest in PREMCOR (1,526,567 shares) to OXY USA Inc., a Delaware
corporation ("OXY USA"), as a contribution to capital and desires to contribute
a 20% portion of the value of the Ownership Interest in PREMCOR (381,642 shares)
to Placid Oil Company, a Delaware corporation ("PLACID"), as a contribution to
capital;and

     WHEREAS, OXY USA desires to contribute its 80% portion of the value of the
Ownership Interest in PREMCOR to Occidental C.O.B. Partners, a Delaware general
partnership ("C.O.B."), as a contribution to capital; and

     WHEREAS, PLACID desires to contribute its 20% portion of the value of the
Ownership Interest in PREMCOR to C.O.B., as a contribution to capital; and

     NOW, THEREFORE, in consideration of the premises, and for other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties hereto agree as follows:

                                    AGREEMENT

     1. OPC to OPIC. OPC hereby assigns and conveys to OPIC of all of the
Ownership Interest as a contribution to the capital of OPIC; and OPIC hereby
accepts and acknowledges the transfer of the Ownership Interest.

2. OPIC to OOGHC. OPIC hereby assigns and conveys to OOGHC of all of the Ownership Interest as a contribution to the capital of OOGHC; and OOGHC hereby accepts and acknowledges the transfer of the Ownership Interest. 3. OOGHC to OXY USA. OOGHC hereby assigns and conveys to OXY USA of 80% of the Ownership Interest as a contribution to the capital of OXY USA; and OXY USA hereby accepts and acknowledges the transfer of 80% of the Ownership Interest. 4. OOGHC to PLACID. OOGHC hereby assigns and conveys to OXY USA of 20% of the Ownership Interest as a contribution to the capital of PLACID; and PLACID hereby accepts and acknowledges the transfer of 20% of the Ownership Interest. 5. OXY USA to C.O.B. OXY USA hereby assigns and conveys to C.O.B. of 80% of the Ownership Interest as a contribution to the capital of C.O.B.; and C.O.B. hereby accepts and acknowledges the transfer of 80% of the Ownership Interest. 6. PLACID to C.O.B. PLACID hereby assigns and conveys to C.O.B. of 20% of the Ownership Interest as a contribution to the capital of C.O.B.; and C.O.B. hereby accepts and acknowledges the transfer of 20% of the Ownership Interest. 7. The parties agree to take all such actions, including executing and delivering all such documents and certificates as may be deemed necessary or appropriate evidence the assignments and conveyances and to carry out the intent and purposes of this Agreement. IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be executed and delivered by one of their duly authorized officers as of the 27th day of May, 2005. OCCIDENTAL PETROLEUM CORPORATION By /s/ J. R. HAVERT ------------------------------------- J. R. Havert Vice President and Treasurer OCCIDENTAL PETROLUEM INVESTMENT CO. By /s/ RONALD K. TAKEUCHI ------------------------------------- Ronald K. Takeuchi Assistant Treasurer 2

OCCIDENTAL OIL AND GAS HOLDING CORPORATION By /s/ J. R. HAVERT ------------------------------------- J. R. Havert Vice President and Treasurer OXY USA INC. By /s/ RONALD K. TAKEUCHI ------------------------------------- Ronald K. Takeuchi Assistant Treasurer PLACID OIL COMPANY By /s/ RONALD K. TAKEUCHI ------------------------------------- Ronald K. Takeuchi Assistant Treasurer OCCIDENTAL C.O.B. PARTNERS OXY USA INC. (AS MANAGING PARTNER) By /s/ J. R. HAVERT ------------------------------------- J. R. Havert Vice President and Treasurer 3