<PAGE>

                                    FORM 6-K

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                        Report of Foreign Private Issuer
                    Pursuant to Rule 13a - 16 or 15d - 16 of
                       the Securities Exchange Act of 1934

For the month of:  September 2000              Commission File Number:  1-12384



                               SUNCOR ENERGY INC.
                              (Name of registrant)

                             112 FOURTH AVENUE S.W.
                                   P.O. BOX 38
                        CALGARY, ALBERTA, CANADA, T2P 2V5

Indicate by check mark whether the registrant files or will file annual reports
under cover of Form 20-F or Form 40-F:

        Form 20-F                                 Form 40-F     X
                  ---------                                 ---------


Indicate by check mark whether the registrant by furnishing the information
contained in this Form is also thereby furnishing the information to the SEC
pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934:

        Yes                                       No            X
                  ---------                                 ---------


If "Yes" is marked, indicate the number assigned to the registrant in connection
with Rule 12g3-2(b):

         N/A


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                                  EXHIBIT INDEX

<TABLE>
<CAPTION>
       EXHIBIT          DESCRIPTION OF EXHIBIT
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<S>                     <C>
EXHIBIT 1               MATERIAL CHANGE REPORT
</TABLE>


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                                    EXHIBIT 1


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                             MATERIAL CHANGE REPORT

ITEM 1    REPORTING ISSUER

          Suncor Energy Inc.
          112 Fourth Avenue S.W.
          Box 38
          Calgary, Alberta
          T2P 2V5

ITEM 2    DATE OF MATERIAL CHANGE

          September 5, 2000

ITEM 3    PRESS RELEASE

          A Press Release with respect to the material change was issued by
          Suncor Energy Inc. on September 5, 2000.

ITEM 4    SUMMARY OF MATERIAL CHANGE
          (ALL DOLLAR AMOUNTS ARE EXPRESSED IN CANADIAN DOLLARS)

          Suncor Energy Inc. ("Suncor") announced on September 5, 2000 that it
          plans to resolve operational issues as well as concerns about
          environmental and social impacts at its Stuart joint venture oil shale
          demonstration project in Australia, which will require an expenditure
          on the part of Suncor of $13 million and potentially up to $22 million
          to improve plant performance. The next stage of development of the
          project will be put on hold until such issues and concerns are
          addressed.

          In addition, the board of directors of Suncor agreed to an after tax
          write down of $80 million of its Stuart Oil Shale Project, reflecting
          increased costs and delayed oil production. Future expenditures at the
          oil shale plant will be expensed against earnings.

ITEM 5    FULL DESCRIPTION OF MATERIAL CHANGE

          Suncor announced on September 5, 2000 that it plans to resolve
          operational issues as well as concerns about environmental and social
          impacts at its Stuart joint venture oil shale demonstration project in
          Australia, which will require an expenditure on the part of Suncor of
          $13 million and potentially up to $22 million to improve plant
          performance. The next stage of development of the project will be put
          on hold until such issues and concerns are addressed.

          In addition, the board of directors of Suncor agreed to an after tax
          write down of $80 million of its Stuart Oil Shale Project, reflecting
          increased costs and delayed oil production. Future expenditures at the
          oil shale plant will be expensed against earnings.

          Suncor has been investing in oil shale technology since 1997 when
          Suncor and its joint venture partners began constructing an oil shale
          demonstration plant near Gladstone, Australia. Over the last year,
          operational and environmental issues have delayed commissioning and
          Suncor has undertaken tests to determine the extent of the additional
          work needed to improve operational performance.

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                                       2


          Suncor's first priority is to operate the plant reliably and address
          community concerns about plant emissions and noise, and it will put
          further stages of development on hold until these operational
          challenges are resolved. The plant upgrades could take until April
          2001 to complete.

          Suncor anticipates that once commissioning is finished, it could need
          an additional six to nine months of operational experience to
          demonstrate the technology before making longer term investment
          decisions.

          In addition to resolving operational issues at the Australian plant,
          sustainability issues must be addressed if oil shale development on a
          commercial scale is to be successful over the long term.

          Key criteria to be applied by Suncor in evaluating the commercial
          potential of oil shale include:

          - a mandate from local, regional and national governments and the
            public to develop oil shale

          - establishing performance standards acceptable to stakeholders that
            address the environmental and social dimensions of oil shale
            development

          - greenhouse gas management plans that align with future national and
            international commitments to address the risk of climate change

          - the capability to generate shareholder value

          Suncor operates the oil shale project in Gladstone, Australia, on
          behalf of its joint venture with Southern Pacific Petroleum NL and
          Central Pacific Minerals NL.

          Suncor's plans as described in this item comprise forward looking
          information subject to certain risks and uncertainties, known and
          unknown. Actual future results may differ materially. This forward
          looking information regarding Suncor's future plans, including cost
          estimates, is preliminary and remains subject to change in response to
          factors that could include stakeholder consultation, the regulatory
          process, detailed engineering work, technical issues, technological
          capabilities, new legislation, and competitive and general economic
          factors and conditions. Further discussion of the risks, uncertainties
          and other factors that could affect these plans and any actual results
          are described in Suncor's annual information form, annual report to
          shareholders and other documents filed with regulatory authorities.

ITEM 6    RELIANCE ON CONFIDENTIALITY SECTION OF THE ACT

          Not applicable

ITEM 7    OMITTED INFORMATION

          Not Applicable

ITEM 8    FURTHER INFORMATION

          For further information relating to the foregoing, contact Michael W.
          O'Brien, Suncor's Executive Vice President, Corporate Development and
          Chief Financial Officer, at 403-269-8111.

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                                       3


ITEM 9    STATEMENT OF SENIOR OFFICER

          The foregoing accurately discloses the material change referred to
          herein.

DATED at Calgary, Alberta, this 5th day of September, 2000.


"MICHAEL W. O'BRIEN"
-----------------------------------------------
MICHAEL W. O'BRIEN
Executive Vice President, Corporate Development
and Chief Financial Officer


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                                   SIGNATURES

Pursuant to the requirements 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.


                                      SUNCOR ENERGY INC.

Date: September 6, 2000               By: "MICHAEL W. O'BRIEN"
                                          ------------------------------------
                                          MICHAEL W. O'BRIEN
                                          Executive Vice President,
                                          Corporate Development and Chief
                                          Financial Officer