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

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2023-10-24</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001896675</rptOwnerCik>
            <rptOwnerName>KIAMILEV PHENIX Q.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O:  WD-40 COMPANY</rptOwnerStreet1>
            <rptOwnerStreet2>9715 BUSINESSPARK AVENUE</rptOwnerStreet2>
            <rptOwnerCity>SAN DIEGO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>92131</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>true</isOfficer>
            <officerTitle>VP, General Counsel &amp; Corp Sec</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>false</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2023-10-24</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>157</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2151</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Shares withheld pursuant to mandatory provisions of Restricted Stock Unit (RSU) Award Agreement(s) in satisfaction of tax withholding obligations upon vesting of 453 RSUs.</footnote>
        <footnote id="F2">Total includes 1,507 unvested RSUs and 224 shares held in the WD-40 Company Profit Sharing / 401(k) Plan.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Ann T. Nguyen, attorney-in-fact for Phenix Q. Kiamilev</signatureName>
        <signatureDate>2023-10-26</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0508
4
2023-10-24
0000105132
WD 40 CO
WDFC
0001896675
KIAMILEV PHENIX Q.
C/O:  WD-40 COMPANY
9715 BUSINESSPARK AVENUE
SAN DIEGO
CA
92131
true
VP, General Counsel & Corp Sec
false
Common Stock
2023-10-24
4
F
0
157
D
2151
D
Shares withheld pursuant to mandatory provisions of Restricted Stock Unit (RSU) Award Agreement(s) in satisfaction of tax withholding obligations upon vesting of 453 RSUs.
Total includes 1,507 unvested RSUs and 224 shares held in the WD-40 Company Profit Sharing / 401(k) Plan.
Ann T. Nguyen, attorney-in-fact for Phenix Q. Kiamilev
2023-10-26