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

    <schemaVersion>X0407</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2023-06-14</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>9715 BUSINESSPARK AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2></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>true</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2023-06-14</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>420</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>200</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2323</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Trust</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2498</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F3"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The reported sales transaction was effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on November 7, 2022.</footnote>
        <footnote id="F2">Under the 2007 Olsem Family Trust, the reporting person shares voting power and investment discretion with her spouse.</footnote>
        <footnote id="F3">Total includes: (i) 539 shares of restricted Common Stock received upon settlement of performance share units or PSUs, (ii) 1,870 unvested RSUs, and (iii) 89 vested deferred
performance units or DPUs, which are Common Stock equivalents.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Phenix Q. Kiamilev, as attorney-in-fact for Patricia Q. Olsem</signatureName>
        <signatureDate>2023-06-16</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0407
4
2023-06-14
0000105132
WD 40 CO
WDFC
0001784383
Olsem Patricia Q
9715 BUSINESSPARK AVENUE
SAN DIEGO
CA
92131
true
Division President, Americas
true
Common Stock
2023-06-14
4
S
0
420
200
D
2323
I
By Trust
Common Stock
2498
D
The reported sales transaction was effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on November 7, 2022.
Under the 2007 Olsem Family Trust, the reporting person shares voting power and investment discretion with her spouse.
Total includes: (i) 539 shares of restricted Common Stock received upon settlement of performance share units or PSUs, (ii) 1,870 unvested RSUs, and (iii) 89 vested deferred
performance units or DPUs, which are Common Stock equivalents.
Phenix Q. Kiamilev, as attorney-in-fact for Patricia Q. Olsem
2023-06-16