<PAGE>
                                                                    Exhibit 4.53


                               SIXTEENTH AMENDMENT

                  SIXTEENTH AMENDMENT, dated as of September 28, 2001 (this
"AMENDMENT"), to and under the Amended and Restated Senior Loan Agreement, dated
as of June 30, 2000 (as heretofore amended, supplemented or otherwise modified,
the "SENIOR LOAN AGREEMENT"), among ANC RENTAL CORPORATION, a Delaware
corporation (the "COMPANY"), the several Lenders from time to time parties
thereto, LEHMAN BROTHERS INC., as sole advisor, sole lead arranger and sole book
manager, and LEHMAN COMMERCIAL PAPER INC., as syndication agent and as
administrative agent (in such capacity, the "ADMINISTRATIVE AGENT").

                              W I T N E S S E T H:

                  WHEREAS, in light of recent events affecting the Company's
business, prospects and financial condition the Company has requested that the
Lenders defer an imminent principal repayment and amend certain provisions of
the Senior Loan Agreement; and

                  WHEREAS, the Lenders have agreed to defer such repayment and
amend the Senior Loan Agreement, but only upon the terms and subject to the
conditions set forth below;

                  NOW, THEREFORE, in consideration of the premises and mutual
agreements contained herein, and for other valuable consideration, the receipt
of which is hereby acknowledged, the Company, the Lenders and the Agents hereby
agree as follows:

                  1. DEFINITIONS. All terms defined in the Senior Loan Agreement
shall have such defined meanings when used herein unless otherwise defined
herein.

                  2. AMENDMENT OF SECTION 1.1 (DEFINED TERMS). Section 1.1 of
the Credit Agreement is hereby amended by adding the following new defined term
in its appropriate alphabetical order:

                  ""GM PROPOSALS": proposals to be made to General Motors
         Corporation regarding potential equity or debt investments or any
         potential fee reduction, operating concessions or other forms of
         support".

                  3. AMENDMENT OF SECTION 2.5 (OPTIONAL AND MANDATORY
PREPAYMENTS). Section 2.5(c) of the Senior Loan Agreement is hereby amended by
deleting "on September 30, 2001" therein and substituting in lieu thereof "on
November 30, 2001".

                  4. AMENDMENT OF SECTION 5.1 (FINANCIAL STATEMENTS). Section
5.1 of the Senior Loan Agreement is hereby amended by (i) deleting the word
"and" at the end clause (a) thereof, (ii) deleting the semicolon at the end of
clause (b) thereof and substituting in lieu thereof "; and" and (iii) adding the
following new clause (c) at the end thereof:

                  "(c) as soon as available, but in any event not later than 10
         Business Days after the end of each calendar month occurring during
         each fiscal year of the Company,


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                                                                               2


         commencing on October 12, 2001, the unaudited consolidated balance
         sheets of the Company and its subsidiaries as at the end of such month
         and the related unaudited consolidated statements of income and of cash
         flows for such month and the portion of the fiscal year through the end
         of such month, setting forth in each case in comparative form (i) the
         figures as of the end of and for the corresponding period in the
         previous year and (ii) the figures as of the end of and for the
         corresponding period as contemplated in the Company's business plan
         delivered to the Lenders on or about June 15, 2001 or, on and after
         delivery thereof, any subsequent business and/or restructuring plan
         delivered to the Lenders pursuant to Section 5.2(i), in each case
         certified by a Responsible Officer as being fairly stated in all
         material respects (subject to normal year-end audit adjustments);".

                  5. AMENDMENT OF SECTION 5.2 (CERTIFICATES; OTHER INFORMATION).
Section 5.2 of the Senior Loan Agreement is hereby amended by: (a) deleting the
reference in the introductory clause thereof to "clause (h)" and substituting in
lieu thereof "clause (k)" and (b) relettering clause (d) thereof as clause (k)
and adding new clauses (d), (e), (f), (g), (h), (i) and (j) immediately after
clause (c) thereof as follows:

                  "(d) on or before Monday of each calendar week, commencing on
         October 1, 2001:

                           (i) a statement, in detail reasonably satisfactory to
                  the Administrative Agent, of consolidated cash flows for the
                  Company and its Subsidiaries for the immediately preceding
                  calendar week, including without limitation, detail as to the
                  aggregate amount of capital expenditures and any payments in
                  excess of $1,000,000 to any Person made during such week;

                           (ii) a forecast, in detail reasonably satisfactory to
                  the Administrative Agent, of consolidated cash flows for the
                  Company and its Subsidiaries for the period of thirteen
                  consecutive calendar weeks beginning in the week immediately
                  following the week in which such forecast is delivered,
                  including without limitation, detail with respect to the
                  following information incorporated into such forecast: fleet
                  size, fleet mix and the aggregate amount of credit enhancement
                  provided in respect of maintenance of the fleet and in respect
                  of any Indebtedness, surety and other obligations of the
                  Company or any Subsidiary thereof, together with a comparison
                  of such amounts to the amount for the same period during the
                  immediately preceding fiscal year of the Company; and

                           (iii) a consolidated report, in detail reasonably
                  satisfactory to the Administrative Agent, of accounts
                  receivable for the immediately preceding week of the
                  businesses conducted by each of National Car Rental System,
                  Inc. and Alamo Rent-A-Car, LLC and their Subsidiaries;

                   (e) on or before the fifteenth day of each calendar month
         commencing on October 15, 2001, a forecast, in detail reasonably
         satisfactory to the Administrative Agent, of consolidated cash flows
         for the Company and its Subsidiaries for the period of 12 consecutive
         calendar months beginning in the month immediately following the



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                                                                               3


         month in which such forecast is delivered, including the assumptions
         based upon which such forecast was prepared in respect of fleet size,
         fleet mix and the aggregate amount of credit enhancement provided in
         respect of maintenance of the fleet and in respect of any Indebtedness,
         surety and other obligations of the Company or any Subsidiary thereof;

                  (f) on or before the tenth Business Day of each calendar month
         commencing on October 12, 2001, a consolidated report, in detail
         reasonably satisfactory to the Administrative Agent, of accounts
         receivable and payable (including agings) for the immediately preceding
         month of the Company and its Subsidiaries;

                  (g) as soon as possible, but in any event within one Business
         Day after the distribution thereof to senior management of the Company
         or any Subsidiary thereof, internal reports of the operations of the
         Company and its Subsidiaries, including without limitation, (i)
         internal reports known as the "Daily Flash Report", which shall include
         detail by brand (i.e., Alamo and National) as to revenue, utilization,
         fleet size, rental volumes and pricing, and comparisons of any such
         information to levels for prior periods, (ii) reports detailed by brand
         (i.e., Alamo and National) as to advanced booking and comparisons of
         any such information to levels for prior periods and (iii) reports as
         to performance of the Alamo Local Markets Division and International
         Division of the Company;

                  (h) on or before the twentieth day of each calendar month,
         commencing on October 20, 2001:

                           (i) detail and summary relating to the valuation of
                  the fleet and information as to the outstanding Indebtedness
                  of the Company and its Subsidiaries, in each case prepared by
                  the Company in the ordinary course of business for, or
                  provided to any other lender, creditor or bond provider (or
                  any affiliate of any of the foregoing); it being understood
                  that the foregoing requirement shall be satisfied by delivery
                  of the Company's servicer reports for its domestic fleet
                  financing;

                           (ii) updated forecasts, projections or business plans
                  for the remainder of the then-current fiscal year of the
                  Company and the next following fiscal year for, or provided to
                  any other lender, creditor or bond provider (or any affiliate
                  of any of the foregoing);

                           (iii) information as to any past or pending
                  significant events or transactions that are material to the
                  Company or any Subsidiary thereof; PROVIDED that the Company
                  shall not be obligated to deliver confidentiality agreements,
                  financial advisory engagement letters, financial advisory fee
                  letters, non-binding letters of interest, bids, commitment
                  letters for commercial lending or high yield financings, or
                  non-binding letters of intent, each to the extent they are by
                  their terms confidential (collectively, "CONFIDENTIAL
                  AGREEMENTS"); and

                           (iv) any other or similar material information or
                  material data that the Company has furnished to any other any
                  other lender, creditor or bond



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                                                                               4


                  provider (or any affiliate of any of the foregoing); PROVIDED
                  that the Company shall not be obligated to deliver any
                  Confidential Agreements;

                           (i) as soon as available but in any event within one
                  Business Day after distribution thereof to senior management
                  of the Company, any restructuring plan or updated business
                  plan prepared by, for or on behalf of the Company or any
                  Subsidiary thereof;

                           (j) on or before October 15, 2001, the GM Proposals
                  and, as promptly as possible after the occurrence of any
                  material discussions with General Motors Corporation in
                  respect of the GM Proposals, updates as to the progress of
                  such discussions; and".

         6. AMENDMENT OF SECTION 5.7 (NOTICES). Section 5.7 of the Senior Loan
Agreement is hereby amended by (i) deleting the word "and" at the end of clause
(e) thereof, (ii) deleting the period at the end of clause (f) thereof and
substituting in lieu thereof "; and" and (iii) adding a new clause (g) at the
end thereof as follows:

                           "(g) as soon as possible but in no event later than
         the day in which any such payment occurs, any payments in an aggregate
         amount exceeding $1,000,000 made on such day by the Company or any of
         its Subsidiaries to any Person, except for any such payments in respect
         of (i) state or payroll taxes, (ii) remittals of insurance premiums,
         (iii) remittals of travel agent commissions and (iv) ordinary course
         payments to Perot Systems, Inc.".

         7. AMENDMENT OF SECTION 5 OF THE SENIOR LOAN AGREEMENT (AFFIRMATIVE
COVENANTS). Section 5 of the Senior Loan Agreement is hereby amended by adding
at the end thereof new Sections 5.16, 5.17 and 5.18 as follows:

                           "5.16. PURSUIT OF TRANSACTIONS. Continue to pursue
         strategic alternatives for the Company and its Subsidiaries as
         described in the Company's Form 8-K report dated August 2, 2001,
         including, without limitation, transactions proposed or under
         discussion prior to September 19, 2001, and transactions that may be
         proposed after September 19, 2001, in each case providing for the sale,
         upon commercially reasonable terms, of all of, or discrete portions of,
         the business of the Company and its Subsidiaries or for the investment
         in the Company of additional equity.

                           5.17. CRISIS MANAGER. Continue to retain William N.
         Plamondon as a crisis manager (or a replacement crisis manager
         reasonably satisfactory to the Administrative Agent), which crisis
         manager shall be permitted to communicate directly with the
         Administrative Agent and the Company's board of directors to, among
         other things, (a) assist the Company and its Subsidiaries with (i) the
         strategic and operational decisions of the Company and its Subsidiaries
         as requested by the board of directors of the Company, (ii) the
         modification and enhancement of the management information systems and
         reporting systems of the Company and its Subsidiaries and (iii) the
         management of and communications with its creditors and other parties,
         (b) supplement the treasury and finance staff of the Borrower and its
         Subsidiaries as needed and (c) make recommendations to conserve and
         generate cash and liquidity for the Company and its Subsidiaries.



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                                                                               5


                           5.18. SALES OF PROPERTY. Continue to pursue the sale
         on commercially reasonable terms of property owned by the Company or
         any Subsidiary thereof which is neither material nor necessary to the
         operations of the business of the Company and its Subsidiaries.".

         8. AMENDMENT OF SECTION 6.13 (LIMITATION ON BUSINESS ACTIVITIES).
Section 6.13 of the Senior Loan Agreement is hereby amended by adding at the end
thereof immediately before the period the following: "PROVIDED, HOWEVER, the
Company will not, and the Company will not permit any of its Restricted
Subsidiaries to, directly or indirectly, extend or expand the business conducted
by the Alamo Local Market Division of the Company".

         9. AMENDMENT OF SECTION 7 (EVENTS OF DEFAULT). Section 7(e) of the
Credit Agreement is hereby amended by adding immediately after "this Section 7"
in the parenthetical therein "or in Sections 5.16, 5.17 or 5.18".

         10. REPRESENTATIONS; NO DEFAULT. On and as of the date hereof, and
after giving effect to this Amendment, (a) the Company certifies that no Default
or Event of Default has occurred or is continuing, and (b) the Company confirms,
reaffirms and restates that the representations and warranties set forth in
Section 3 of the Senior Loan Agreement and in the other Loan Documents are true
and correct in all material respects, PROVIDED that (i) the references to the
Senior Loan Agreement therein shall be deemed to be references to this Amendment
and to the Senior Loan Agreement as amended by this Amendment and (ii) for
purposes of this Section 10 the representation and warranty contained in (A)
Section 3.2 of the Senior Loan Agreement shall be deemed modified to change the
date referred to therein from December 31, 1999 to September 17, 2001 and (B)
Section 3.18 of the Senior Loan Agreement shall be deemed modified to change the
last sentence thereof to replace the word "There" in the beginning of such
sentence with "Since September 17, 2001, there".

         11. CONDITIONS TO EFFECTIVENESS. This Amendment shall become effective
as of the date hereof upon satisfaction of the following:

                  (a) the Administrative Agent shall have received counterparts
         of this Amendment, duly executed and delivered by a duly authorized
         officer of the Company;

                  (b) the Administrative Agent shall have received executed
         Lender Consent Letters, substantially in the form of Exhibit A hereto,
         from Lenders whose consent is required pursuant to Section 9.1 of the
         Senior Loan Agreement; and

                  (c) the Administrative Agent shall have received an executed
         Acknowledgment and Consent, in the form set forth at the end of this
         Amendment, from each Loan Party other than the Company.

         12. LIMITED AMENDMENT. Except as expressly amended herein, the Senior
Loan Agreement shall continue to be, and shall remain, in full force and effect.
This



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                                                                               6


Amendment shall not be deemed to be a waiver of, or consent to, or a
modification or amendment of, any other term or condition of the Senior Loan
Agreement or any other Loan Document or to prejudice any other right or rights
which the Lenders may now have or may have in the future under or in connection
with the Senior Loan Agreement or any of the instruments or agreements referred
to therein, as the same may be amended from time to time.

         13. COUNTERPARTS. This Amendment may be executed by one or more of the
parties hereto in any number of separate counterparts (which may include
counterparts delivered by facsimile transmission) and all of said counterparts
taken together shall be deemed to constitute one and the same instrument.

         14. GOVERNING LAW. THIS AMENDMENT SHALL BE GOVERNED BY, AND CONSTRUED
AND INTERPRETED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK.



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                                                                               7




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

                                       ANC RENTAL CORPORATION



                                       By: /s/ Howard D. Schwartz
                                           -------------------------------------
                                           Name:  Howard D. Schwartz
                                           Title: Sr. Vice President & Secretary



                                       LEHMAN COMMERCIAL PAPER INC.,
                                       as Administrative Agent


                                       By: /s/ G. Andrew Keith
                                           -------------------------------------
                                           Name:  G. Andrew Keith
                                           Title: Authorized Signatory



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                                                                               8



                           ACKNOWLEDGMENT AND CONSENT

                  Each of the undersigned parties to the Subsidiary Guarantee,
dated as of June 30, 2000 and as amended, supplemented or otherwise modified
from time to time, made by the undersigned in favor of Lehman Commercial Paper
Inc., as Administrative Agent, for the benefit of the Lenders, hereby (a)
consents to the transactions contemplated by the foregoing Amendment to the
Senior Loan Agreement and (b) acknowledges and agrees that the guarantees
contained in the Subsidiary Guarantee and in the other Loan Documents are, and
shall remain, in full force and effect after giving effect to such Amendment and
all prior modifications to the Senior Loan Agreement.

                                       ALAMO RENT-A-CAR (CANADA), INC.
                                       LIABILITY MANAGEMENT COMPANIES HOLDING,
                                        INC.
                                       NATIONAL CAR RENTAL LICENSING, INC.
                                       NATIONAL CAR RENTAL SYSTEM, INC.
                                       REPUBLIC GUY SALMON PARTNER, INC.
                                       REPUBLIC INDUSTRIES AUTOMOTIVE RENTAL
                                        GROUP (BELGIUM) INC.
                                       SPIRIT RENT-A-CAR, INC.
                                       ALAMO RENT-A-CAR MANAGEMENT, LP
                                          By: ARC-GP, Inc., its general partner
                                       ANC COLLECTOR CORPORATION
                                       ANC FINANCIAL, LP
                                           By: ANC Financial GP Corporation,
                                               its general partner
                                       ARC-GP, INC.
                                       ARC-TM, INC.
                                       NCR AFFILIATE SERVICER, INC.
                                       NCRAS MANAGEMENT, LP
                                           By: NCRAS-GP, Inc., its general
                                               partner
                                       NCRAS-GP, INC.
                                       SRAC MANAGEMENT, LP
                                           By: SRAC-GP, Inc., its general
                                                partner
                                       SRAC-GP, INC.
                                       SRAC-TM, INC.

                                       By: /s/ Leland F. Wilson
                                           -------------------------------------
                                           Name:  Leland F. Wilson
                                           Title: Vice President & Treasurer

                                       ALAMO RENT-A-CAR, LLC

                                       By: /s/ Kathleen W. Kyle
                                           -------------------------------------
                                           Name:  Kathleen W. Kyle
                                           Title: Sr. Vice President & Treasurer




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                                                                               9


                                       ANC FINANCIAL CORPORATION
                                       ANC FINANCIAL PROPERTIES LLC
                                       ANC INFORMATION TECHNOLOGY HOLDING, INC.
                                       ANC INFORMATION TECHNOLOGY, INC.
                                       ANC INFORMATION TECHNOLOGY, L.P.
                                           By: ANC INFORMATION TECHNOLOGY, INC.,
                                               its general partner
                                       ANC IT COLLECTOR CORPORATION
                                       ARC-TM PROPERTIES LLC
                                       NCR AFFILIATE SERVICER PROPERTIES, LLC



                                       By: /s/ Leland F. Wilson
                                           -------------------------------------
                                           Name:  Leland F. Wilson
                                           Title: Vice President & Treasurer


<PAGE>
                                                                       EXHIBIT A
                                                          to Sixteenth Amendment

                              LENDER CONSENT LETTER

                             ANC RENTAL CORPORATION
                   AMENDED AND RESTATED SENIOR LOAN AGREEMENT
                            DATED AS OF JUNE 30, 2000


To:      Lehman Commercial Paper Inc.
         3 World Financial Center
         New York, New York  10285

Ladies and Gentlemen:

                  Reference is made to the Amended and Restated Senior Loan
Agreement, dated as of June 30, 2000 (the "SENIOR LOAN AGREEMENT"), among ANC
RENTAL CORPORATION, a Delaware corporation (the "COMPANY"), the Lenders parties
thereto, LEHMAN COMMERCIAL PAPER INC., as Administrative Agent, and others.
Unless otherwise defined herein, capitalized terms used herein and defined in
the Senior Loan Agreement are used herein as therein defined.

                  The Company has requested that the Lenders consent to amend
the Senior Loan Agreement on the terms described in the Amendment to which a
form of this Lender Consent Letter is attached as Exhibit A (the "AMENDMENT").

                  Pursuant to Section 9.1 of the Senior Loan Agreement, the
undersigned Lender hereby consents to the execution by the Agents of the
Amendment.

                                       Very truly yours,

                                       -----------------------------------------
                                       (NAME OF LENDER)


                                       By:
                                           -------------------------------------
                                           Name:
                                           Title:

Dated as of ____________ __, 2001