<PAGE>   1
                                                                    EXHIBIT 4(c)

                       FIFTH AMENDMENT TO LOAN AGREEMENT

         THIS FIFTH AMENDMENT TO LOAN AGREEMENT (this "Fifth Amendment") is made
and entered into as of the 2nd day of February, 1999, by and among SERVICE
TRANSPORT COMPANY, a Texas corporation ("Service Transport Company"), ADAMS
RESOURCES EXPLORATION CORPORATION, a Delaware corporation ("Exploration"),
BUCKLEY MINING CORPORATION, a Kentucky corporation ("Buckley Mining"), CJC
LEASING, INC., a Kentucky corporation ("CJC"), CLASSIC COAL CORPORATION, a
Delaware corporation ("Classic Coal"), ADA MINING CORPORATION, a Texas
corporation ("Ada Mining") and BAYOU CITY PIPELINES, INC., a Texas corporation
formerly known as Bayou City Barge Lines, Inc. ("Bayou City"), each with offices
and place of business at 5 Post Oak Place, 4400 Post Oak Parkway, 27th Floor,
Houston, Texas 77027 (Service Transport Company, Exploration, Buckley Mining,
CJC, Classic Coal, Ada Mining and Bayou City are hereinafter individually called
a "Borrower" and collectively called the "Borrowers"), and NATIONSBANK, N.A., a
national banking association (the "Lender"), successor in interest by merger to
NationsBank of Texas, N.A. (the "Original Lender").

         WHEREAS, the Borrowers, Ada Crude Oil Company ("Ada Crude Oil") and Ada
Resources, Inc. ("Ada Resources"), (collectively referred to as the "Original
Borrowers") and the "Original Lender entered into that certain Loan Agreement
dated October 27, 1993, which Loan Agreement was amended by that certain First
Amendment to Loan Agreement dated October 27, 1994 among the Original Borrowers
and the Original Lender, that certain Second Amendment to Loan Agreement dated
December 29, 1995 among the Original Borrowers and the Original Lender, that
certain Third Amendment to Loan Agreement dated January 27, 1997 among the
Original Borrowers and the Original Lender and that certain Fourth Amendment to
Loan Agreement dated September 30th, 1997 among the Original Borrowers and the
Original Lender (as amended, the "Loan Agreement"); and

         WHEREAS, due to the assignment of the assets and assumption of
liabilities of Ada Crude Oil and Ada Resources, such parties are no longer
parties under the Loan Agreement; and

         WHEREAS, the Borrowers and the Lender desire to make certain amendments
to the terms and provisions of the Loan Agreement, as set forth herein.

         NOW, THEREFORE, FOR AND IN CONSIDERATION of the mutual covenants and
agreements contained herein, the parties hereto agree as follows:

         1.     The first sentence of Section 1.3(a) of the Loan Agreement is 
deleted in its entirety, and the following is substituted in its place:

         The Lender, during the period from the date of the Third Amendment 
         through October 27, 2000, subject to the terms and conditions of this
         Agreement, agrees (i) to make loans to the


<PAGE>   2


         Borrowers pursuant to a revolving credit and term loan facility up to
         but not in excess of the lesser of $ 10,000,000.00 or the amount of the
         Tranche A Borrowing Base and (ii) to make additional loans to the
         Borrowers pursuant to a revolving credit and term loan facility up to
         but not in excess of the lesser of $5,000,000.00 or the amount of the
         Tranche B Borrowing Base.

         2.     The fourth and fifth sentences of Section 1.3(b) of the Loan
Agreement are deleted in their entirety, and the following is substituted in 
their place:

         Commencing October 31, 2000, a principal payment shall be made on each
         Note on the last day of each October, January, April and July in an
         amount equal to one-twelfth (1/12th) of the principal amount
         outstanding under such Note at the close of Lender's business on
         October 27, 2000. All unpaid principal and accrued and unpaid interest
         on the Notes shall be due and payable on or before October 27, 2003.

         3.     The closing of the transactions contemplated by this Fifth
Amendment is subject to the satisfaction of the following conditions:

                (a) All legal matters incident to the transactions herein
         contemplated shall be satisfactory to Gardere Wynne Sewell & Riggs,
         L.L,P., counsel to the Lender;

                (b) The Lender shall have received a fully executed copy of this
         Fifth Amendment and a Notice as to Written Agreement; and

                (c) The Lender shall have received an executed copy OF
         resolutions of the Board of Directors of each of the Borrowers and the
         Guarantor, in form and substance satisfactory to the Lender,
         authorizing the execution, delivery and performance of this Fifth
         Amendment and all documents, instruments and certificates referred to
         herein.

         4.     Each of the Borrowers hereby reaffirms each of its 
representations, warranties, covenants and agreements set forth in the Loan
Agreement with the same force and effect as if each were separately stated
herein and made as of the date hereof. Except as amended hereby, the Loan
Agreement shall remain unchanged, and the terms, conditions and covenants of the
Loan Agreement shall continue and be binding upon the parties hereto.

         5.     Each of the Borrowers hereby agrees that its liability under any
and all documents and instruments executed by it as security for the
Indebtedness (including, without limitation, the Mortgages, the Security
Agreements, the Collateral Assignment and the Pledges) shall not be reduced,
altered, limited, lessened or in any way affected by the execution and delivery
of this Fifth Amendment or any of the instruments or documents referred to
herein, except as specifically set forth herein or therein, that all of such
documents and instruments are hereby renewed, extended, ratified, confirmed and
carried forward by the Borrowers in all respects, that all of such documents and
instruments shall remain in full force and effect and are and shall remain
enforceable against the

                                       -2-


<PAGE>   3



Borrowers in accordance with their terms and that all of such documents and
instruments shall cover all indebtedness of the Borrowers to the Lender
described in the Loan Agreement as amended hereby.

          6.    Each of the terms defined in the Loan Agreement is used in this
Fifth Amendment with the same meaning, except as otherwise indicated in this
Fifth Amendment. Each of the terms defined in this Fifth Amendment is used in
the Loan Agreement with the same meaning, except as otherwise indicated in the
Loan Agreement.

          7.    THIS FIFTH AMENDMENT SHALL BE DEEMED TO BE A CONTRACT UNDER,
SUBJECT TO, AND SHALL BE CONSTRUED FOR ALL PURPOSES IN ACCORDANCE WITH THE LAWS
OF THE STATE OF TEXAS.

          8.    THE LOAN AGREEMENT, AS AMENDED, REPRESENTS THE FINAL AGREEMENT
BETWEEN THE PARTIES AND MAY NOT BE CONTRADICTED BY EVIDENCE OF PRIOR,
CONTEMPORANEOUS OR SUBSEQUENT ORAL AGREEMENTS OF THE PARTIES.

                THERE ARE NO UNWRITTEN ORAL AGREEMENTS BETWEEN THE PARTIES.

          IN WITNESS WHEREOF, the parties have caused this Fifth Amendment to be
executed by their duly authorized officers as of the day and year first above
written.

                              SERVICE TRANSPORT COMPANY


                              By: /s/ R. B. ABSHIRE
                                 ----------------------------------------
                                 Name: R. B. Abshire
                                      -----------------------------------
                                 Title:  Treasurer
                                       ----------------------------------


                              ADAMS RESOURCES EXPLORATION
                              CORPORATION

                              By: /s/ R. B. ABSHIRE
                                 ----------------------------------------
                                 Name: R. B. Abshire
                                      -----------------------------------
                                 Title:  Treasurer
                                       ----------------------------------


                                       -3-



<PAGE>   4



                              BUCKLEY MINING CORPORATION


                              By: /s/ R. B. ABSHIRE
                                 ----------------------------------------
                                 Name: R. B. Abshire
                                      -----------------------------------
                                 Title:  Treasurer
                                       ----------------------------------


                              CJC LEASING, INC.


                              By: /s/ R. B. ABSHIRE
                                 ----------------------------------------
                                 Name: R. B. Abshire
                                      -----------------------------------
                                 Title:  Treasurer
                                       ----------------------------------


                              CLASSIC COAL CORPORATION


                              By: /s/ R. B. ABSHIRE
                                 ----------------------------------------
                                 Name: R. B. Abshire
                                      -----------------------------------
                                 Title:  Treasurer
                                       ----------------------------------


                              ADA MINING CORPORATION


                              By: /s/ R. B. ABSHIRE
                                 ----------------------------------------
                                 Name: R. B. Abshire
                                      -----------------------------------
                                 Title:  Treasurer
                                       ----------------------------------


                              BAYOU CITY PIPELINES, INC.


                              By: /s/ R. B. ABSHIRE
                                 ----------------------------------------
                                 Name: R. B. Abshire
                                      -----------------------------------
                                 Title:  Treasurer
                                       ----------------------------------



                                       -4-



<PAGE>   5


                              NATIONSBANK, N.A.
          
                              By: /s/ JAMES R. ALLRED
                                 ----------------------------------------
                                 Name: James R. Allred
                                      -----------------------------------
                                 Title: Senior Vice President
                                       ----------------------------------

         Guarantor joins in the execution of this Fifth Amendment to evidence
that it hereby agrees and consents to all of the matters contained in this Fifth
Amendment and further agrees that (i) its liability under that certain Guaranty
Agreement dated October 27, 1993, executed by Guarantor for the benefit of the
Lender, as the same may be amended or modified from time to time (the 
"Guaranty") shall not be reduced, altered, limited, lessened or in any way
affected by the execution and delivery of this Fifth Amendment or any of the
instruments or documents referred to herein by the parties hereto, except as
specifically set forth herein or therein, (ii) the Guaranty is hereby renewed,
extended, ratified, confirmed and carried forward in all respects, (iii) the
Guaranty is and shall remain in full force and effect and is and shall remain
enforceable against Guarantor in accordance with its terms and (iv) the Guaranty
shall cover all indebtedness of the Borrowers to the Lender described in the
Loan Agreement as amended hereby.

                              ADAMS RESOURCES & ENERGY, INC.


                              By: /s/ R. B. ABSHIRE
                                 ----------------------------------------
                                 Name: R. B. Abshire
                                      -----------------------------------
                                 Title:  Vice President
                                       ----------------------------------


                                      -5-