<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2007-06-08</periodOfReport>

    <issuer>
        <issuerCik>0000095304</issuerCik>
        <issuerName>SUNOCO INC</issuerName>
        <issuerTradingSymbol>SUN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001178437</rptOwnerCik>
            <rptOwnerName>FAIRBAIRN URSULA F</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1735 MARKET STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>PHILADELPHIA</rptOwnerCity>
            <rptOwnerState>PA</rptOwnerState>
            <rptOwnerZipCode>19103-7583</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Deferred Share Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2007-06-08</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>23.932</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>79.966</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F2"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>23.932</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6983.075</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Phantom Stock Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2007-06-08</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>46.005</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>79.966</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F2"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>46.005</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>13423.67</value>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F2">Not Applicable</footnote>
        <footnote id="F3">Total of 6,983.075 Restricted Share Units beneficially owned following reported transaction (15.915 Restricted Share Units under Sunoco, Inc.'s Directors' Deferred Compensation Plan I and 8.017 Restricted Share Units under Sunoco, Inc.'s Directors' Deferred Compensation Plan II).</footnote>
        <footnote id="F4">Total of 13,423.670 Phantom Stock Units beneficially owned following reported transaction (35.127 Phantom Stock Units under Sunoco, Inc.'s Directors' Deferred Compensation Plan I and 10.878 Phanton Stock Units under Sunoco, Inc.'s Directors' Deferred Compensation Plan II).</footnote>
        <footnote id="F1">Conversion rate is 1 for 1.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>John J. DiRocco, Jr., Attorney-in-fact for Ursula O. Fairbairn</signatureName>
        <signatureDate>2007-06-12</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0202
4
2007-06-08
0000095304
SUNOCO INC
SUN
0001178437
FAIRBAIRN URSULA F
1735 MARKET STREET
PHILADELPHIA
PA
19103-7583
1
0
0
0
Deferred Share Units
2007-06-08
4
A
0
23.932
79.966
A
Common Stock
23.932
6983.075
D
Phantom Stock Units
2007-06-08
4
A
0
46.005
79.966
A
Common Stock
46.005
13423.67
D
Not Applicable
Total of 6,983.075 Restricted Share Units beneficially owned following reported transaction (15.915 Restricted Share Units under Sunoco, Inc.'s Directors' Deferred Compensation Plan I and 8.017 Restricted Share Units under Sunoco, Inc.'s Directors' Deferred Compensation Plan II).
Total of 13,423.670 Phantom Stock Units beneficially owned following reported transaction (35.127 Phantom Stock Units under Sunoco, Inc.'s Directors' Deferred Compensation Plan I and 10.878 Phanton Stock Units under Sunoco, Inc.'s Directors' Deferred Compensation Plan II).
Conversion rate is 1 for 1.
John J. DiRocco, Jr., Attorney-in-fact for Ursula O. Fairbairn
2007-06-12