<PAGE>
 
                                                                   EXHIBIT 10.13

               FOURTH AMENDMENT dated as of November 3, 1998 (this "Fourth
                                                                    ------
               Amendment"), to the Credit Agreement dated as of December 13,
               ---------                                                    
               1995 (as amended prior to the date hereof, the "Credit
                                                               ------
               Agreement"), among Star Gas Propane, L.P., a Delaware limited
               partnership (the "Borrower"), the lenders party thereto, The
                                 --------                                  
               First National Bank of Boston (now known as BankBoston, N.A.), as
               Administrative Agent (the "Administrative Agent"), and
                                          --------------------       
               NationsBank, N.A., as Documentation Agent (the "Documentation
                                                               -------------
               Agent", and together with the Administrative Agent, the
               -----                                                  
               "Agents").
                ------   

     The Borrower has requested the Agents and the Lenders to make certain
changes to the Credit Agreement.  The parties hereto have agreed, subject to the
terms and conditions hereof, to amend the Credit Agreement as provided herein.

     Capitalized terms used and not otherwise defined herein shall have the
meanings assigned to such terms in the Credit Agreement (the Credit Agreement,
as amended by, and together with, this Fourth Amendment, and as hereinafter
amended, modified, extended or restated from time to time, being called the
"Amended Agreement").
------------------   

     Accordingly, the parties hereto hereby agree as follows:

     SECTION 1.01.  Amendment to Section 4.03.  Section 4.03(a) of the Credit
                    -------------------------                                
Agreement is hereby deleted in its entirety and the following is substituted in
lieu thereof:

          "(a) At the time of and immediately after any Tranche B Revolving
Credit Borrowing made or any Tranche B Letter of Credit issued (i) on or before
June 30, 1999, the Leverage Ratio as of the date of such Borrowing or issuance
(after giving affect to the acquisition or Growth-Related Capital Expenditure
for which such Borrowing or Letter of Credit is being used) shall be no greater
than 5.00:1.00 and (ii) after June 30, 1999, the Leverage Ratio as of the date
of such Borrowing or issuance (after giving affect to the acquisition or Growth-
Related Capital Expenditure for which such Borrowing or Letter of Credit is
being used) shall be no greater than 4.50:1.00; and, in the case of each such
Borrowing or issuance of each such Letter of Credit, the Borrower shall have
prepared and furnished to the Agents prior to such Borrowing or issuance pro
forma financial statements demonstrating the fulfillment of such condition to
the satisfaction of the Agents.  For purposes of calculating the Leverage Ratio
as required by this Section 4.03(a), Consolidated Cash Flow for the Reference
Period shall mean the greater of (A) Consolidated Cash Flow for the most recent
period of four consecutive fiscal quarters prior to the date of determination
and (B) 50% of Consolidated Cash Flow for the most recent period of eight
consecutive fiscal quarters prior to the date of determination."

     SECTION 1.02.  Amendment to Section 6.31.  Section 6.31(a) of the Credit
                    -------------------------                                
Agreement is hereby deleted in its entirety and the following is hereby
substituted in lieu thereof:

          "(a) The Borrower will not permit the ratio on any day (the "date of
     determination") of (i) Total Funded Debt as of the last day of the
     Reference Period with respect to such date of determination to (ii)
     Consolidated Cash Flow for such Reference Period to be greater than the
     ratio set forth below opposite the calendar period during which such date
     of determination occurs:

 
<PAGE>
 
<TABLE>
<CAPTION>
Calendar Period                        Ratio
---------------                        -----
<S>                                    <C>
        January 1, 1996 through        5.00:1.00
        June 30, 1997
 
        July 1, 1997 through           4.75:1.00
        September 30, 1997
 
        October 1, 1997 through        4.95:1.00
        December 31, 1997
 
        January 1, 1998 through        5.00:1.00
        June 30, 1999

        After June 30, 1999            4.50:1.00"
</TABLE> 


     SECTION 1.03.  Amendment to Section 9.01.
                    ------------------------- 

     9.01(c) of the Credit Agreement is hereby deleted in its entirety and the
following is hereby deleted in its entirety and the following is hereby
substituted in lieu thereof:

"(c) if to the Documentation Agent, to it at Three Allen Center, 333 Clay
     Street, Suite 4550, Houston, Texas 77002-4103, Attention of Daryl Patterson
     (Telecopy no. (713) 651-4808), with a copy to Fennebresque, Clark, Swindell
     & Hay, at NationsBank Corporate Center, 100 North Tryon Street, Suite 2900,
     Charlotte, NC  28202-4011, Attention of Marvin L. Rogers (Telecopy No.
     (704) 347-3838; and "

     SECTION 1.04.  Representations and Warranties.  The Borrower hereby
                    ------------------------------                      
represents and warrants to each of the Agents and the Lenders, as follows:

          (a)  The representations and warranties set forth in Article III of
     the Amended Agreement, and in each other Loan Document, are true and
     correct in all material respects on and as of the date hereof and on and as
     of the Fourth Amendment Effective Date (as hereinafter defined) with the
     same effect as if made on and as of the date hereof or the Fourth Amendment
     Effective Date, as the case may be, except to the extent such
     representations and warranties expressly relate solely to an earlier date.

          (b)  Each of the Borrower and the Subsidiaries is in compliance with
     all the terms and conditions of the Amended Agreement and the other Loan
     Documents on its part to be observed or performed and no Default or Event
     of Default has occurred or is continuing.

          (c)  The execution, delivery and performance by the Borrower of this
     Fourth Amendment have been duly authorized by the Borrower.

          (d)  This Fourth Amendment constitutes the legal, valid and binding
     obligation of the Borrower, enforceable against it in accordance with its
     terms.

                                       2
<PAGE>
 
          (e)  The execution, delivery and performance by the Borrower of this
     Fourth Amendment (i) will not violate (A) any provision of law, statute,
     rule or regulation, or of the agreement of limited partnership of the
     Borrower, (B) any order of any Governmental Authority or (C) any provision
     of any indenture, agreement or other instrument to which the Borrower is a
     party or by which it or any of its property may be bound and (ii) do not
     require any consents under, result in a breach of or constitute (with
     notice or lapse of time or both) a default or give rise to increased,
     additional, accelerated or guaranteed rights of any Person under any such
     indenture, agreement or other instrument.

     SECTION 1.05.   Effectiveness.  This Fourth Amendment shall become
                     -------------                                     
effective only upon satisfaction of the following conditions precedent (the
first date upon which each such condition has been satisfied being herein called
the "Fourth Amendment Effective Date"):
     -------------------------------   

          (a)  the Administrative Agent shall have received duly executed
     counterparts of this Fourth Amendment which, when taken together, bear the
     authorized signatures of the Borrower and the Required Lenders.

          (b)  The Agents shall be satisfied that the representations and
     warranties set forth in Section 1.03 are true and correct on and as of the
     Fourth Amendment Effective Date.

          (c)  There shall not be any action pending or any judgment, order or
     decree in effect which, in the judgment of the Agents or the Lenders, is
     likely to restrain, prevent or impose materially adverse conditions upon
     performance by the Borrower of its obligations under the Amended Agreement.

          (d)  The Agents shall have received such other documents, legal
     opinions, instruments and certificates relating to this Fourth Amendment as
     they shall reasonably request and such other documents, legal opinions,
     instruments and certificates shall be satisfactory in form and substance to
     the Agents and the Lenders. All corporate and other proceedings taken or to
     be taken in connection with this Fourth Amendment and all documents
     incidental thereto, whether or not referred to herein, shall be
     satisfactory in form and substance to the Agents and the Lenders.

          (e)  The Borrower shall have paid all fees and expenses referred to in
     Section 1.07 of this Fourth Amendment.

     SECTION 1.06.  APPLICABLE LAW.  THIS FOURTH AMENDMENT SHALL BE GOVERNED BY,
                    --------------                                              
AND CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK, EXCEPT TO
THE EXTENT THAT THE FEDERAL LAWS OF THE UNITED STATES OF AMERICA MAY APPLY.

     SECTION 1.07.  Expenses.  The Borrower shall pay all reasonable out-of-
                    --------                                               
pocket expenses incurred by the Agents and the Lenders in connection with the
preparation, negotiations execution, delivery and enforcement of this Fourth
Amendment, including, but not limited to, the reasonable fees and disbursements
of counsel.

     SECTION 1.08.  Counterparts.  This Fourth Amendment may be executed in any
                    ------------                                               
number of counterparts, each of which shall constitute an original but all of
which when taken together shall constitute but one agreement.

                                       3
<PAGE>
 
     SECTION 1.09.  Loan Documents.  Except as expressly set forth herein, the
                    --------------                                            
amendments provided herein shall not by implication or otherwise limit,
constitute a waiver of, or otherwise affect the rights and remedies of the
Lenders, the Agents, the Trustee or the other Secured Parties under the Amended
Agreement or any other Loan Document, nor shall they constitute a waiver of any
Default or Event of Default, nor shall they alter, modify, amend or in any way
affect any of the terms, conditions, obligations, covenants or agreements
contained in the Amended Agreement or any other Loan Document.  Each of the
amendments provided herein shall apply and be effective only with respect to the
provisions of the Amended Agreement specifically referred to by such amendments.
Except as expressly amended herein, the Amended Agreement and the other Loan
Documents shall continue in full force and effect in accordance with the
provisions thereof.  As used in the Amended Agreement, the terms "Agreement",
"herein", "hereinafter", "hereunder", "hereto" and words of similar import shall
mean, from and after the date hereof, the Amended Agreement.

     IN WITNESS WHEREOF, the parties hereto have caused this Fourth Amendment to
be duly executed by duly authorized officers, all as of the date first above
written.

                         STAR GAS PROPANE, L.P., as Borrower

                         By:  Star Gas Corporation, its General Partner


                         by____________________________________________
                         Name:
                         Title:


                         BANKBOSTON, N.A.,
                         as Administrative Agent and as a Lender


                         by____________________________________________
                         Name:
                         Title:


                         NATIONSBANK, N.A., as Documentation Agent
                         and as a Lender


                         by____________________________________________
                         Name:
                         Title:

                                       4