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

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2024-05-09</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001951273</rptOwnerCik>
            <rptOwnerName>HYZER SARA KATHLEEN</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>VP, Finance &amp; CFO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>false</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2024-05-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>213</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>232.83</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2676</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Total includes:  (i) 1,868 unvested RSUs and (ii) shares held in Reporting Person's WD-40 Company Profit Sharing / 401(k) Plan account.  On May 1, 2023, the 401(k) plan administrator unilaterally liquidated 12 shares of WDFC at $187.59 per share to return excess 401(k) contributions for tax year 2022 to the Reporting Person, and a net of 370 shares (rounded to the nearest whole share) are now held in such account as of May 10, 2024.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Ann T. Nguyen, attorney-in-fact for Sara K. Hyzer</signatureName>
        <signatureDate>2024-05-10</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0508
4
2024-05-09
0000105132
WD 40 CO
WDFC
0001951273
HYZER SARA KATHLEEN
C/O: WD-40 COMPANY
9715 BUSINESSPARK AVE.
SAN DIEGO
CA
92131
true
VP, Finance & CFO
false
Common Stock
2024-05-09
4
P
0
213
232.83
A
2676
D
Total includes:  (i) 1,868 unvested RSUs and (ii) shares held in Reporting Person's WD-40 Company Profit Sharing / 401(k) Plan account.  On May 1, 2023, the 401(k) plan administrator unilaterally liquidated 12 shares of WDFC at $187.59 per share to return excess 401(k) contributions for tax year 2022 to the Reporting Person, and a net of 370 shares (rounded to the nearest whole share) are now held in such account as of May 10, 2024.
Ann T. Nguyen, attorney-in-fact for Sara K. Hyzer
2024-05-10