CVNA: amended insider filing

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

    <schemaVersion>X0609</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2026-07-31</periodOfReport>

    <dateOfOriginalSubmission>2026-08-04</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001690820</issuerCik>
        <issuerName>CARVANA CO.</issuerName>
        <issuerTradingSymbol>CVNA</issuerTradingSymbol>
        <issuerForeignTradingSymbol></issuerForeignTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001088011</rptOwnerCik>
            <rptOwnerName>MAROONE MICHAEL E</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerNonUSAddressFlag>false</rptOwnerNonUSAddressFlag>
            <rptOwnerStreet1>C/O CARVANA CO.</rptOwnerStreet1>
            <rptOwnerStreet2>300 E. RIO SALADO PARKWAY</rptOwnerStreet2>
            <rptOwnerCity>TEMPE</rptOwnerCity>
            <rptOwnerState>AZ</rptOwnerState>
            <rptOwnerZipCode>85281</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2026-07-31</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>21153</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>61.69</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>745198</value>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2026-07-31</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>3847</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>62.40</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F5"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>749045</value>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>225000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Michael Maroone Family Partnership, LP</value>
                    <footnoteId id="F4"/>
                    <footnoteId id="F6"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1320</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Family Trust FBO Michael E. Maroone</value>
                    <footnoteId id="F4"/>
                    <footnoteId id="F7"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The Reporting Person realized short-swing profits under Section 16(b) as a result of the purchase reported on this Form 4 being matched against the sale of 5 shares of the Issuer's Class A common stock within the preceding six months. Prior to filing, the Reporting Person paid Carvana Co. the full $64.87 in disgorgeable profits; no further disgorgement is owed.</footnote>
        <footnote id="F2">The price reported above reflects the volume weighted average purchase price. The Reporting Person undertakes to provide, upon request by the SEC staff, the Issuer, or a security holder of the Issuer, full information regarding the number of shares sold at each price.</footnote>
        <footnote id="F3">This transaction was executed in multiple trades at prices ranging from $61.28 to $62.25, inclusive.</footnote>
        <footnote id="F4">Due to a calculation error, the Form 4 filed August 4, 2026 incorrectly reported the shares of Class A common stock held directly by the Reporting Person and the Form 4 further did not reflect the five for one forward stock split conducted by the Issuer on May 7, 2026. This amended Form 4 is filed solely to reflect the corrected ownership holdings.</footnote>
        <footnote id="F5">This transaction was executed in multiple trades at prices ranging from $62.29 to $62.50, inclusive.</footnote>
        <footnote id="F6">Represents shares held directly by the Michael Maroone Family Partnership, LP, an entity controlled by the Reporting Person.</footnote>
        <footnote id="F7">Represents shares held directly by the Family Trust FBO Michael E. Maroone, where the Reporting Person is beneficiary and trustee.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Paul Breaux, by Power of Attorney for Michael E. Maroone</signatureName>
        <signatureDate>2026-10-05</signatureDate>
    </ownerSignature>
</ownershipDocument>