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

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2024-10-22</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>2024-10-22</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>429</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4231</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2024-10-22</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>344</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3887</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2024-10-22</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>73</value>
                    <footnoteId id="F3"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3814</value>
                    <footnoteId id="F4"/>
                </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 843 RSUs.</footnote>
        <footnote id="F2">Shares withheld pursuant to mandatory provisions of Market Share Unit (MSU) Award Agreement in satisfaction of tax withholding obligations upon vesting of 677 MSUs.</footnote>
        <footnote id="F3">Shares withheld pursuant to mandatory provisions of Performance Stock Unit (PSU) Award Agreement in satisfaction of tax withholding obligations upon vesting of 144 PSUs.</footnote>
        <footnote id="F4">Total includes:  (i) 2,202 unvested RSUs, (ii) 71 shares of restricted Common Stock received upon settlement of PSUs, and (iii) 355 shares held in Reporting Person's WD-40 Company Profit Sharing / 401(k) Plan account.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Ann T. Nguyen, attorney-in-fact for Sara K. Hyzer</signatureName>
        <signatureDate>2024-10-24</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0508
4
2024-10-22
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
2024-10-22
4
F
0
429
D
4231
D
Common Stock
2024-10-22
4
F
0
344
D
3887
D
Common Stock
2024-10-22
4
F
0
73
D
3814
D
Shares withheld pursuant to mandatory provisions of Restricted Stock Unit (RSU) Award Agreement(s) in satisfaction of tax withholding obligations upon vesting of 843 RSUs.
Shares withheld pursuant to mandatory provisions of Market Share Unit (MSU) Award Agreement in satisfaction of tax withholding obligations upon vesting of 677 MSUs.
Shares withheld pursuant to mandatory provisions of Performance Stock Unit (PSU) Award Agreement in satisfaction of tax withholding obligations upon vesting of 144 PSUs.
Total includes:  (i) 2,202 unvested RSUs, (ii) 71 shares of restricted Common Stock received upon settlement of PSUs, and (iii) 355 shares held in Reporting Person's WD-40 Company Profit Sharing / 401(k) Plan account.
Ann T. Nguyen, attorney-in-fact for Sara K. Hyzer
2024-10-24