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                                                                      EXHIBIT 11
 
                    MAPCO INC. AND CONSOLIDATED SUBSIDIARIES
 
                STATEMENT RE: COMPUTATION OF PER SHARE EARNINGS
                    (IN MILLIONS, EXCEPT PER SHARE AMOUNTS)
 
<TABLE>
<CAPTION>
                                                    THREE MONTHS              TWELVE MONTHS
                                                 ENDED DECEMBER 31,         ENDED DECEMBER 31,
                                                ---------------------    ------------------------
                                                  1996         1995         1996          1995
                                                ---------    --------    -----------    ---------
<S>                                             <C>          <C>         <C>            <C>
PRIMARY EARNINGS PER SHARE
Computation for Consolidated Statements of
  Income
  Net income(a)...............................  $   42.3     $    8.0     $   97.5      $   74.7
                                                ========     ========     ========      ========
  Weighted average common shares
     outstanding(a)(d)........................      56.1         58.9         57.3          59.5
  Common stock equivalents (stock options)....        --           --           --            --
                                                --------     --------     --------      --------
  Weighted average common shares
     outstanding(a)(d)........................      56.1         58.9         57.3          59.5
                                                ========     ========     ========      ========
  Primary earnings per common
     share(a)(c)(d)...........................  $   0.75     $   0.14     $   1.70      $   1.26
                                                ========     ========     ========      ========
Additional Primary Computation
  Net income(a)...............................  $   42.3     $    8.0     $   97.5      $   74.7
                                                ========     ========     ========      ========
  Weighted average common shares
     outstanding(a)(d)........................      56.1         58.9         57.3          59.5
  Dilutive effect of outstanding options......       0.6          0.1          0.3           0.1
                                                --------     --------     --------      --------
  Weighted average common shares outstanding,
     as adjusted(d)...........................      56.7         59.0         57.6          59.6
                                                ========     ========     ========      ========
  Primary earnings per common share, as
     adjusted(b)(d)...........................  $   0.75     $   0.14     $   1.69      $   1.25
                                                ========     ========     ========      ========
FULLY DILUTED EARNINGS PER COMMON SHARE
Additional Fully Diluted Computation
  Net income(a)...............................  $   42.3     $    8.0     $   97.5      $   74.7
                                                ========     ========     ========      ========
  Weighted average common shares
     outstanding(a)(d)........................      56.1         58.9         57.3          59.5
  Dilutive effect of outstanding options......       0.7          0.2          0.4           0.1
                                                --------     --------     --------      --------
  Weighted average common shares outstanding,
     as adjusted(d)...........................      56.8         59.1         57.7          59.6
                                                ========     ========     ========      ========
  Primary earnings per common share, as
     adjusted(b)(d)...........................  $   0.74     $   0.14     $   1.69      $   1.25
                                                ========     ========     ========      ========
</TABLE>
 
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(a) These figures agree with the related amounts in the consolidated statements
    of income.
 
(b) This calculation is submitted in accordance with the Securities Exchange Act
    of 1934 Release No. 9083, although not required by footnote 2 to paragraph
    14 of APB Opinion No. 15 because it results in dilution of less than 3%.
 
(c) In 1996 and 1995, stock options are not included in the earnings per share
    computation included in MAPCO's consolidated statements of income because
    the dilutive effect is less than 3%.
 
(d) On September 10, 1996, the Board of Directors authorized a two-for-one stock
    split effected in the form of a stock dividend from shares held as treasury
    stock, which was distributed on September 30, 1996, to shareholders of
    record on September 16, 1996. All references in this Exhibit 11 to number of
    shares and per share amounts of the Company's common stock have been
    retroactively restated to reflect the increased number of shares
    outstanding.