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

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2023-10-05</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001784383</rptOwnerCik>
            <rptOwnerName>Olsem Patricia Q</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>Division President, Americas</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>false</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2023-10-05</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>964</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5246</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Trust</value>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>539</value>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Represents a grant of restricted stock units (RSUs) under the WD-40 Company 2016 Stock Incentive Plan.  Except as otherwise provided in the RSU award agreement, the RSUs vest annually over 3 years.</footnote>
        <footnote id="F2">Total includes: (i) 2,834 unvested RSUs and (ii) 89 vested deferred performance units or DPUs, which are Common Stock equivalents.</footnote>
        <footnote id="F3">Under the 2007 Olsem Family Trust, the reporting person shares voting power and investment discretion with her spouse.</footnote>
        <footnote id="F4">Represents shares of restricted Common Stock received upon settlement of performance share units or PSUs.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Ann T. Nguyen, attorney-in-fact for Patricia Q. Olsem</signatureName>
        <signatureDate>2023-10-10</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0508
4
2023-10-05
0000105132
WD 40 CO
WDFC
0001784383
Olsem Patricia Q
C/O:  WD-40 COMPANY
9715 BUSINESSPARK AVE.
SAN DIEGO
CA
92131
true
Division President, Americas
false
Common Stock
2023-10-05
4
A
0
964
A
5246
I
By Trust
Common Stock
539
D
Represents a grant of restricted stock units (RSUs) under the WD-40 Company 2016 Stock Incentive Plan.  Except as otherwise provided in the RSU award agreement, the RSUs vest annually over 3 years.
Total includes: (i) 2,834 unvested RSUs and (ii) 89 vested deferred performance units or DPUs, which are Common Stock equivalents.
Under the 2007 Olsem Family Trust, the reporting person shares voting power and investment discretion with her spouse.
Represents shares of restricted Common Stock received upon settlement of performance share units or PSUs.
Ann T. Nguyen, attorney-in-fact for Patricia Q. Olsem
2023-10-10