<PAGE>   1
 
                                                                      EXHIBIT 11
 
                          FINA, INC. AND SUBSIDIARIES
 
               COMPUTATION OF RATIO OF EARNINGS TO FIXED CHARGES
                  FOR THE FIVE YEARS ENDING DECEMBER 31, 1996
                                 (IN THOUSANDS)
 
FINA, INC. CONSOLIDATED
 
<TABLE>
<CAPTION>
                                            1997       1996       1995       1994       1993
                                          --------   --------   --------   --------   --------
<S>                                       <C>        <C>        <C>        <C>        <C>
Net pre-tax earnings....................  $188,207   $228,262   $161,078   $152,357   $ 96,115
Fixed charges...........................    58,945     55,086     61,561     56,010     69,106
Adjustment for capitalized interest.....    (7,764)    (4,889)    (7,873)    (2,422)    (3,234)
                                          --------   --------   --------   --------   --------
  Earnings as adjusted (A)..............  $239,388   $278,459   $214,766   $205,945   $161,987
                                          ========   ========   ========   ========   ========
Fixed Charges:
Interest Expense:.......................  $ 45,048   $ 43,137   $ 50,707   $ 47,023   $ 58,190
Rents under leases representative of an
  interest factor (1)...................    13,897     11,949     10,854      8,987     10,916
                                          --------   --------   --------   --------   --------
Fixed Charges as adjusted (B)...........  $ 58,945   $ 55,086   $ 61,561   $ 56,010   $ 69,106
                                          ========   ========   ========   ========   ========
          RATIO OF EARNINGS TO FIXED
            CHARGES:
            (A) DIVIDED BY (B)..........       4.1        5.1        3.5        3.7        2.3
                                          ========   ========   ========   ========   ========
</TABLE>
 
FOCC CONSOLIDATED
 
<TABLE>
<CAPTION>
                                            1997       1996       1995       1994       1993
                                          --------   --------   --------   --------   --------
<S>                                       <C>        <C>        <C>        <C>        <C>
Net pre-tax earnings....................  $176,434   $204,670   $152,824   $145,819   $100,147
Fixed charges...........................    57,911     54,980     61,420     55,863     68,747
Adjustment for capitalized interest.....    (7,673)    (4,852)    (7,788)    (2,371)    (3,198)
                                          --------   --------   --------   --------   --------
  Earnings as adjusted (A)..............  $226,672   $254,798   $206,456   $199,311   $165,696
                                          ========   ========   ========   ========   ========
Fixed Charges:
Interest Expense........................    45,048   $ 43,134   $ 50,706   $ 47,021   $ 58,182
Rents under leases representative of an
  interest factor(1)....................    12,863     11,846     10,714      8,842     10,565
                                          --------   --------   --------   --------   --------
  Fixed Charges as adjusted (B).........  $ 57,911   $ 54,980   $ 61,420   $ 55,863   $ 68,747
                                          ========   ========   ========   ========   ========
          RATIO OF EARNINGS TO FIXED
            CHARGES:
            (A) DIVIDED BY (B)..........       3.9        4.6        3.4        3.6        2.4
                                          ========   ========   ========   ========   ========
</TABLE>
 
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(1) Management of the Company believes approximately one-third of rental and
    lease expense is representative of the interest component of rent expense.