<?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>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>2024-10-22</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>255</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3289</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Trust</value>
                </natureOfOwnership>
            </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>238</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3051</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Trust</value>
                </natureOfOwnership>
            </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>38</value>
                    <footnoteId id="F3"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3013</value>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Trust</value>
                    <footnoteId id="F5"/>
                </natureOfOwnership>
            </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 712 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 665 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 106 PSUs.</footnote>
        <footnote id="F4">Total includes:  (i) 1,422 unvested RSUs, (ii) 68 shares of restricted Common Stock received upon settlement of PSUs, and (iii) 209 shares held in Reporting Person's WD-40 Company Profit Sharing / 401(k) Plan account.</footnote>
        <footnote id="F5">Beneficial ownership had previously been reported as Direct and is now being reported as Indirect.  Under The Kiamilev Family Trust established on October 5, 2012, Reporting Person shares voting power and investment discretion with her spouse.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Ann T. Nguyen, attorney-in-fact for Phenix Q. Kiamilev</signatureName>
        <signatureDate>2024-10-24</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0508
4
2024-10-22
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
2024-10-22
4
F
0
255
D
3289
I
By Trust
Common Stock
2024-10-22
4
F
0
238
D
3051
I
By Trust
Common Stock
2024-10-22
4
F
0
38
D
3013
I
By Trust
Shares withheld pursuant to mandatory provisions of Restricted Stock Unit (RSU) Award Agreement(s) in satisfaction of tax withholding obligations upon vesting of 712 RSUs.
Shares withheld pursuant to mandatory provisions of Market Share Unit (MSU) Award Agreement in satisfaction of tax withholding obligations upon vesting of 665 MSUs.
Shares withheld pursuant to mandatory provisions of Performance Stock Unit (PSU) Award Agreement in satisfaction of tax withholding obligations upon vesting of 106 PSUs.
Total includes:  (i) 1,422 unvested RSUs, (ii) 68 shares of restricted Common Stock received upon settlement of PSUs, and (iii) 209 shares held in Reporting Person's WD-40 Company Profit Sharing / 401(k) Plan account.
Beneficial ownership had previously been reported as Direct and is now being reported as Indirect.  Under The Kiamilev Family Trust established on October 5, 2012, Reporting Person shares voting power and investment discretion with her spouse.
Ann T. Nguyen, attorney-in-fact for Phenix Q. Kiamilev
2024-10-24