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

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2024-11-13</periodOfReport>

    <issuer>
        <issuerCik>0000105132</issuerCik>
        <issuerName>WD 40 CO</issuerName>
        <issuerTradingSymbol>WDFC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001253564</rptOwnerCik>
            <rptOwnerName>NOBLE WILLIAM B</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O:  WD-40 COMPANY</rptOwnerStreet1>
            <rptOwnerStreet2>9715 BUSINESSPARK AVE.</rptOwnerStreet2>
            <rptOwnerCity>SAN DIEGO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>92131</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>true</isOfficer>
            <officerTitle>Group Managing Director</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>false</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2024-11-13</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>289.7</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>7999</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Represents average sales price per share; sales prices ranged from $289.17 to $289.85.</footnote>
        <footnote id="F2">Total includes:  (i) 1,025 unvested restricted stock units, (ii) 522 shares of restricted Common Stock received upon settlement of performance stock units, and (iii) 280 vested deferred performance units, which are Common Stock equivalents.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Ann T. Nguyen, attorney-in-fact for William B. Noble</signatureName>
        <signatureDate>2024-11-14</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0508
4
2024-11-13
0000105132
WD 40 CO
WDFC
0001253564
NOBLE WILLIAM B
C/O:  WD-40 COMPANY
9715 BUSINESSPARK AVE.
SAN DIEGO
CA
92131
true
Group Managing Director
false
Common Stock
2024-11-13
4
S
0
1000
289.7
D
7999
D
Represents average sales price per share; sales prices ranged from $289.17 to $289.85.
Total includes:  (i) 1,025 unvested restricted stock units, (ii) 522 shares of restricted Common Stock received upon settlement of performance stock units, and (iii) 280 vested deferred performance units, which are Common Stock equivalents.
Ann T. Nguyen, attorney-in-fact for William B. Noble
2024-11-14