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

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2024-10-03</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>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>Division President, Americas</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>false</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2024-10-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>765</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5607</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Trust</value>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2024-10-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>912</value>
                    <footnoteId id="F4"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F4"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1540</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2024-10-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>164</value>
                    <footnoteId id="F5"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F5"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1704</value>
                    <footnoteId id="F6"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Represents a grant of restricted stock units (RSUs) under the WD-40 Company 2016 Stock Incentive Plan, as amended and restated effective December 12, 2023.  Except as otherwise provided in the RSU award agreement, the RSUs vest annually over 3 years.</footnote>
        <footnote id="F2">Total includes 2,693 unvested RSUs.</footnote>
        <footnote id="F3">Under the 2007 Olsem Family Trust, Reporting Person shares voting power and investment discretion with her spouse.</footnote>
        <footnote id="F4">Represents the vesting of market share units (MSUs) upon certification of market performance achieved.  The 3-year performance cliff vesting MSUs were granted on October 12, 2021 under the WD-40 Company 2016 Stock Incentive Plan and will be settled with Issuer's Common Stock on the date provided for in the MSU award agreement.</footnote>
        <footnote id="F5">Represents the vesting of performance stock units (PSUs) upon certification of fiscal year 2024 performance achieved.  The PSUs were granted on October 5, 2023 under the WD-40 Company 2016 Stock Incentive Plan and will be settled with Issuer's restricted Common Stock on the date provided for in the PSU award agreement.  Reporting Person may not sell such restricted stock before termination of employment.</footnote>
        <footnote id="F6">Total composed of:  (i) 912 shares of Common Stock to be received upon settlement of MSUs, (iii) 703 shares of restricted Common Stock received or to be received upon settlement of PSUs, and (iii) 89 vested deferred performance units or DPUs, which are Common Stock equivalents.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Ann T. Nguyen, attorney-in-fact for Patricia Q. Olsem</signatureName>
        <signatureDate>2024-10-07</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0508
4
2024-10-03
0000105132
WD 40 CO
WDFC
0001784383
Olsem Patricia Q
C/O:  WD-40 COMPANY
9715 BUSINESSPARK AVE.
SAN DIEGO
CA
92131
true
Division President, Americas
false
Common Stock
2024-10-03
4
A
0
765
A
5607
I
By Trust
Common Stock
2024-10-03
4
A
0
912
A
1540
D
Common Stock
2024-10-03
4
A
0
164
A
1704
D
Represents a grant of restricted stock units (RSUs) under the WD-40 Company 2016 Stock Incentive Plan, as amended and restated effective December 12, 2023.  Except as otherwise provided in the RSU award agreement, the RSUs vest annually over 3 years.
Total includes 2,693 unvested RSUs.
Under the 2007 Olsem Family Trust, Reporting Person shares voting power and investment discretion with her spouse.
Represents the vesting of market share units (MSUs) upon certification of market performance achieved.  The 3-year performance cliff vesting MSUs were granted on October 12, 2021 under the WD-40 Company 2016 Stock Incentive Plan and will be settled with Issuer's Common Stock on the date provided for in the MSU award agreement.
Represents the vesting of performance stock units (PSUs) upon certification of fiscal year 2024 performance achieved.  The PSUs were granted on October 5, 2023 under the WD-40 Company 2016 Stock Incentive Plan and will be settled with Issuer's restricted Common Stock on the date provided for in the PSU award agreement.  Reporting Person may not sell such restricted stock before termination of employment.
Total composed of:  (i) 912 shares of Common Stock to be received upon settlement of MSUs, (iii) 703 shares of restricted Common Stock received or to be received upon settlement of PSUs, and (iii) 89 vested deferred performance units or DPUs, which are Common Stock equivalents.
Ann T. Nguyen, attorney-in-fact for Patricia Q. Olsem
2024-10-07