EXHIBIT 10.18


                AMENDMENT TO STOCK AND ASSET PURCHASE AGREEMENT

     AMENDMENT TO STOCK AND ASSET PURCHASE AGREEMENT (this "Amendment") dated
July 31, 1995, among CASTLE ENERGY CORPORATION, a Delaware corporation; INDIAN
REFINING & MARKETING I INC., an Illinois corporation (f/k/a Indian Refining &
Marketing Inc.), INDIAN REFINING I LIMITED PARTNERSHIP, an Illinois limited
partnership (f/k/a Indian Refining Limited Partnership), IP OIL CO., an Illinois
corporation, INDIAN POWERINE L.P., an Illinois limited partnership, and INDIAN
OIL COMPANY, an Illinois corporation; and CORE REFINING CORPORATION, A Delaware
corporation.

     The parties hereto are parties to a Stock and Asset Purchase Agreement
dated May 25, 1995 (the "Purchase Agreement"). Capitalized terms not otherwise
defined herein have the meaning ascribed to them in the Purchase Agreement.

     NOW, THEREFORE, for good and valuable consideration, receipt of which is
hereby acknowledged, the parties hereto agree as follows:

     1.   Section 1.1 of the Purchase Agreement is hereby amended, effective as
          of the date first set forth above, by (i) deleting the defined term
          "Termination Date" in its entirety and (ii) substituting therefor the
          following:

     "Termination Date" shall mean August 15, 1995; provided, that if, on or
before August 15, 1995, CORE shall give notice to Castle that the Issuer has
commenced marketing the first mortgage notes that comprise a portion of the Debt
Financing and that CORE reasonably believes it can obtain the Financing and
consummate the Closing on or before August 31, 1995, the Termination Date shall
be extended to August 31, 1995.

     IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
executed as of the day and year first written above.

                             CORE REFINING CORPORATION

                             By: /s/William S. Sudhaus
                                 ----------------------------------------------
                                 William S. Sudhaus, President

                             CASTLE ENERGY CORPORATION

                             By: /s/Joseph L. Castle II
                                 ----------------------------------------------
                                 Joseph L. Castle II 
                                 Chief Executive Officer





                             INDIAN REFINING & MARKETING I INC.

                             By: /s/David M. Hermes
                                 ----------------------------------------------
                                 David M. Hermes, Senior Vice President- Raw
                                 Material Supply

                             INDIAN REFINING I LIMITED PARTNERSHIP
                             By: Indian Refining & Marketing I Inc.

                             By: /s/David M. Hermes
                                 ----------------------------------------------
                                 David M. Hermes, Senior Vice President- Raw
                                 Material Supply

                             IP OIL CO.

                             By: /s/David M. Hermes
                                 ----------------------------------------------
                                 David M. Hermes, Senior Vice President- Raw
                                 Material Supply 

                             INDIAN POWERINE L.P.
                             By: IP OIL CO.

                             By: /s/David M. Hermes
                                 ----------------------------------------------
                                 David M. Hermes, Senior Vice President- Raw
                                 Material Supply

                             INDIAN OIL COMPANY

                                 By: /s/David M. Hermes
                                 ----------------------------------------------
                                 David M. Hermes, Senior Vice President- Raw
                                 Material Supply 

                                      -2-