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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2006-12-06</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001213296</rptOwnerCik>
            <rptOwnerName>DELANEY TERENCE P</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>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Vice President</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5352</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2006-12-06</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>I</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1461.348</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>68.43</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>698.652</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Spouse (ESOP Trust)</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2006-12-06</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>I</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>3653.368</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>68.43</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6010.632</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>ESOP Trust</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Options (Right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>68.43</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2006-12-06</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F3"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>6000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2008-12-06</value>
            </exerciseDate>
            <expirationDate>
                <value>2016-12-06</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>6000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Disposition by spouse of 1,461.348 share equivalents from the Sunoco, Inc. Common Stock Fund in the Sunoco, Inc. Capital Accumulation Plan (&quot;SunCAP&quot;), pursuant to discretionary transaction exempt under Rule 16b-3(f).</footnote>
        <footnote id="F2">Disposition of 3,653.368 share equivalents from the Sunoco, Inc. Common Stock Fund in the Sunoco, Inc. Capital Accumulation Plan (&quot;SunCAP&quot;), pursuant to discretionary transaction exempt under Rule 16b-3(f).</footnote>
        <footnote id="F3">Stock options (rights to buy Sunoco, Inc. common stock) exercisable two years from the date of grant, pursuant to the Sunoco, Inc. Long Term Performance Enhancement Plan II (LTPEP II), in a transaction exempt under Rule 16b-3.  These stock options were granted with tandem appreciation rights (Limited Rights) that may be exercised for cash only in the event of a change in control of Sunoco, Inc.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>John J. DiRocco, Jr., Attorney-in-fact for Terence P. Delaney</signatureName>
        <signatureDate>2006-12-08</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0202
4
2006-12-06
0000095304
SUNOCO INC
SUN
0001213296
DELANEY TERENCE P
1735 MARKET STREET
PHILADELPHIA
PA
19103-7583
0
1
0
0
Vice President
Common Stock
5352
D
Common Stock
2006-12-06
4
I
0
1461.348
68.43
D
698.652
I
By Spouse (ESOP Trust)
Common Stock
2006-12-06
4
I
0
3653.368
68.43
D
6010.632
I
ESOP Trust
Stock Options (Right to buy)
68.43
2006-12-06
4
A
0
6000
0
A
2008-12-06
2016-12-06
Common Stock
6000
6000
D
Disposition by spouse of 1,461.348 share equivalents from the Sunoco, Inc. Common Stock Fund in the Sunoco, Inc. Capital Accumulation Plan ("SunCAP"), pursuant to discretionary transaction exempt under Rule 16b-3(f).
Disposition of 3,653.368 share equivalents from the Sunoco, Inc. Common Stock Fund in the Sunoco, Inc. Capital Accumulation Plan ("SunCAP"), pursuant to discretionary transaction exempt under Rule 16b-3(f).
Stock options (rights to buy Sunoco, Inc. common stock) exercisable two years from the date of grant, pursuant to the Sunoco, Inc. Long Term Performance Enhancement Plan II (LTPEP II), in a transaction exempt under Rule 16b-3.  These stock options were granted with tandem appreciation rights (Limited Rights) that may be exercised for cash only in the event of a change in control of Sunoco, Inc.
John J. DiRocco, Jr., Attorney-in-fact for Terence P. Delaney
2006-12-08