<PAGE>   1
 
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                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549
 
                                  FORM 10-K/A
                                AMENDMENT NO. 2
 
(MARK ONE)   
  [X]             ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
                   SECURITIES AND EXCHANGE ACT OF 1934 [FEE REQUIRED]
                       FOR THE FISCAL YEAR ENDED DECEMBER 31, 1997

  [ ]           TRANSACTION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
                    SECURITIES EXCHANGE ACT OF 1934 [NO FEE REQUIRED]
 
            FOR THE TRANSITION PERIOD FROM            TO
 
                           COMMISSION FILE NUMBER: 1-4014
 
                                   FINA, INC.
             (Exact name of registrant as specified in its charter)
 
                  DELAWARE                                       13-1820692
       State or other jurisdiction of                         (I.R.S. Employer
       incorporation or organization                        Identification No.)
         FINA PLAZA, DALLAS, TEXAS                                 75206
  (Address of principal executive offices)                       (Zip Code)
 
       Registrant's Telephone Number Including Area Code: (214) 750-2400
 
          Securities registered pursuant to Section 12(b) of the Act:
 
                                                    NAME OF EACH EXCHANGE
            TITLE OF EACH CLASS                      ON WHICH REGISTERED
            -------------------                     ---------------------
    Class A Common Stock $.50 par value            American Stock Exchange
 
          Securities registered pursuant to Section 12(g) of the Act:
 
                                      None
 
INDICATE BY CHECK MARK WHETHER THE REGISTRANT (1) HAS FILED ALL REPORTS REQUIRED
TO BE FILED BY SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 DURING
THE PRECEDING 12 MONTHS (OR FOR SUCH SHORTER PERIOD THAT THE REGISTRANT WAS
REQUIRED TO FILE SUCH REPORTS), AND (2) HAS BEEN SUBJECT TO SUCH FILING
REQUIREMENTS FOR THE PAST 90 DAYS.                 YES  X      NO
                                                       ---        ---
     The aggregate market value of the Class A Common voting stock held by
non-affiliates of the Registrant as of February 11, 1998 was $162,562,360 based
on the highest price of $59.8125 per share as recorded by the American Stock
Exchange.
 
     The number of shares outstanding of each of the issuer's classes of common
stock, as of March 6, 1997:
 
                       CLASS A COMMON STOCK -- 29,231,972
                       CLASS B COMMON STOCK --  2,000,000
 
     Documents Incorporated by Reference: Part III: The Company's Proxy
Statement for Annual Meeting of Stockholders of April 15, 1998
 
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                                    PART IV
 
ITEM 14     EXHIBITS, FINANCIAL STATEMENT SCHEDULES AND REPORTS ON FORM 8-K
 
     (a) The following are incorporated by reference or filed as part of this
Annual Report:
 
        1. and 2. Consolidated Financial Statements and Schedules:
 
             Reference is made to page 13 of this Form 10-K for a list of all
        consolidated financial statements and schedules filed as part of this
        Form 10-K.
 
             No reports on Form 8-K were filed during the last quarter of the
        period covered by this report. However, a Form 8-K was filed on February
        17, 1998 reporting a news release by the Company approving a merger with
        PetroFina S.A. whereby the Company would become an indirect,
        wholly-owned affiliate.
 
        3. Exhibits: (Contained separately and EDGAR filed)
 
<TABLE>
           <S>       <C>
            (2b)     -- Agreement and Plan of Merger
            (3a)     -- The Articles of Incorporation of FINA, Inc.
            (3b)     -- The Bylaws of FINA, Inc.
           (10a)     -- Thrift and Employee Stock Ownership Plan for Employees of
                        American Petrofina, Incorporated
           (10b)     -- Credit Agreements of February 27, 1997 with NationsBank
                        of Texas, N.A., as Agent, as amended February 26, 1998
           (10c)     -- American Petrofina, Incorporated Employee Non-Qualified
                        Stock Option Plan (1979)
           (10d)*    -- Form 11-K Amdel Inc. Employee Investment Plan
           (10e)     -- Form 11-K FINA Capital Accumulation Plan
           (10f)     -- Agreements between FINA, Inc. (formerly American
                        Petrofina, Incorporated) and Ron W. Haddock
           (10g)     -- Employee Stock Ownership Plan of American Petrofina,
                        Incorporated
           (10h)     -- FINA Capital Accumulation Plan as amended
           (10i)     -- FINA Restoration Plan
           (11)      -- Computation of Ratio of Earnings to Fixed Charges
           (19)      -- FINA, Inc.'s Proxy Statement for Annual Meeting of
                        Security Holders on April 15, 1998
           (21)      -- Subsidiaries of the Registrant
           (23)*     -- Independent Auditors' Consent
           (27)      -- Financial Data Schedule
</TABLE>

* Filed herewith
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                                   SIGNATURE
 
     Pursuant to the requirements of Section 13 or 15(d) of the Securities
Exchange Act of 1934, the Registrant has duly caused this Report to be signed on
its behalf by the undersigned, thereunto duly authorized.
 
                                        FINA, Inc.
                                        (Registrant)
 
                                        By:       /s/ CULLEN M. GODFREY
                                           -------------------------------------
                                                     Cullen M. Godfrey
                                           Senior Vice President, Secretary and
                                                      General Counsel
 
Date: April 27, 1998
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                                EXHIBIT INDEX

 
<TABLE>
<CAPTION>

  EXHIBIT                            DESCRIPTION
  -------                            -----------
<S>          <C>                                                         
   (2b)      -- Agreement and Plan of Merger
   (3a)      -- The Articles of Incorporation of FINA, Inc.
   (3b)      -- The Bylaws of FINA, Inc.
  (10a)      -- Thrift and Employee Stock Ownership Plan for Employees of
                American Petrofina, Incorporated
  (10b)      -- Credit Agreements of February 27, 1997 with NationsBank
                of Texas, N.A. as Agent, as amended February 26, 1998
  (10c)      -- American Petrofina, Incorporated Employee Non-Qualified
                Stock Option Plan (1979)
  (10d)*     -- Form 11-K Amdel Inc. Employee Investment Plan
  (10e)      -- Form 11-K FINA Capital Accumulation Plan
  (10f)      -- Agreements between FINA, Inc. (formerly American
                Petrofina, Incorporated) and Ron W. Haddock
  (10g)      -- Employee Stock Ownership Plan of American Petrofina,
                Incorporated
  (10h)      -- FINA Capital Accumulation Plan, as Amended
  (10i)      -- Fina Restoration Plan
  (11)       -- Computation of Ratio of Earnings to Fixed Charges
  (19)       -- FINA, Inc.'s Proxy Statement for Annual Meeting of
                Security Holders to be held April 15, 1998
  (21)       -- Subsidiaries of the Registrant
  (23)*      -- Independent Auditors' Consent
  (27)       -- Financial Data Schedule
</TABLE>

* Filed herewith