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

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2024-04-16</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001691913</rptOwnerCik>
            <rptOwnerName>Brass Steven A</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>
            <isDirector>true</isDirector>
            <isOfficer>true</isOfficer>
            <officerTitle>President and CEO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>false</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2024-04-16</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>432</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>232.22</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>20547</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Total includes: (i) 973 shares of restricted Common Stock received upon settlement of performance share units or PSUs, (ii) 7,500 unvested RSUs, (iii) 108 vested deferred performance units or DPUs, which are common stock equivalents, and (iv) 2,208 shares held in the Reporting Person's WD-40 Company Profit Sharing Plan / 401(k) Plan and Trust account.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Ann T. Nguyen, attorney-in-fact for Steven A. Brass</signatureName>
        <signatureDate>2024-04-17</signatureDate>
    </ownerSignature>
</ownershipDocument>
[{"type": "4", "sequence": "1", "filename": "form4.xml", "secsgml_size_bytes": 3299}]
X0508
4
2024-04-16
0000105132
WD 40 CO
WDFC
0001691913
Brass Steven A
C/O:  WD-40 COMPANY
9715 BUSINESSPARK AVE.
SAN DIEGO
CA
92131
true
true
President and CEO
false
Common Stock
2024-04-16
4
P
0
432
232.22
A
20547
D
Total includes: (i) 973 shares of restricted Common Stock received upon settlement of performance share units or PSUs, (ii) 7,500 unvested RSUs, (iii) 108 vested deferred performance units or DPUs, which are common stock equivalents, and (iv) 2,208 shares held in the Reporting Person's WD-40 Company Profit Sharing Plan / 401(k) Plan and Trust account.
Ann T. Nguyen, attorney-in-fact for Steven A. Brass
2024-04-17