-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 KF5oI4XGBy0gaCeMER861JZksP5yXbyMuU+DpyHg4si0xXCD+8MiJjTZHeYyjguE
 zXFRpHe/q67XFNPiC7T9zg==

<SEC-DOCUMENT>0001140361-04-000371.txt : 20040116
<SEC-HEADER>0001140361-04-000371.hdr.sgml : 20040116
<ACCEPTANCE-DATETIME>20040116155530
ACCESSION NUMBER:		0001140361-04-000371
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20031202
FILED AS OF DATE:		20040116

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			GRINNELL CHARLES W
		CENTRAL INDEX KEY:			0001246220

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-27432
		FILM NUMBER:		04529820

	BUSINESS ADDRESS:	
		STREET 1:		C/O CLEAN DIESEL TECHNOLOGIES INC
		STREET 2:		300 ATLANTIC ST
		CITY:			STAMFORD
		STATE:			CT
		ZIP:			06901
		BUSINESS PHONE:		2033277050

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			CLEAN DIESEL TECHNOLOGIES INC
		CENTRAL INDEX KEY:			0000949428
		STANDARD INDUSTRIAL CLASSIFICATION:	INDUSTRIAL INORGANIC CHEMICALS [2810]
		IRS NUMBER:				061393453
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		300 ATLANTIC ST
		STREET 2:		STE 702
		CITY:			STAMFORD
		STATE:			CT
		ZIP:			06901
		BUSINESS PHONE:		2033277050

	MAIL ADDRESS:	
		STREET 1:		300 ATLANTIC ST
		STREET 2:		STE 702
		CITY:			STAMFORD
		STATE:			CT
		ZIP:			06901
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc1.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>
<periodOfReport>2003-12-02</periodOfReport>
<notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0000949428</issuerCik>
        <issuerName>CLEAN DIESEL TECHNOLOGIES INC</issuerName>
        <issuerTradingSymbol>cdti</issuerTradingSymbol>
</issuer>
<reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001246220</rptOwnerCik>
            <rptOwnerName>GRINNELL CHARLES W</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>300 ATLANTIC STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>STAMFORD</rptOwnerCity>
            <rptOwnerState>X1</rptOwnerState>
            <rptOwnerZipCode>06901</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>1</isDirector>
<isOfficer>1</isOfficer>
<isTenPercentOwner>0</isTenPercentOwner>
<isOther>0</isOther>
<officerTitle>Vice President</officerTitle>
<otherText></otherText>
</reportingOwnerRelationship>
</reportingOwner>
<nonDerivativeTable>
<nonDerivativeHolding>
<securityTitle>
<value>Common Stock</value>
</securityTitle>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>15204</value>
</sharesOwnedFollowingTransaction>
</postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value>
</directOrIndirectOwnership>
<natureOfOwnership>
<value></value>
</natureOfOwnership>
</ownershipNature>
</nonDerivativeHolding>
</nonDerivativeTable>
<derivativeTable>
<derivativeTransaction>
<securityTitle>
<value>Stock Option</value>
</securityTitle>
<conversionOrExercisePrice>
<value>3.07</value>
</conversionOrExercisePrice>
<transactionDate>
<value>2003-12-02</value>
</transactionDate>
<deemedExecutionDate>
</deemedExecutionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>A</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved>
</transactionCoding>
<transactionTimeliness>
<value></value>
</transactionTimeliness>
<transactionAmounts>
<transactionShares>
<value>20000</value>
</transactionShares>
<transactionPricePerShare>
<value>0</value>
</transactionPricePerShare>
<transactionAcquiredDisposedCode>
<value>A</value>
</transactionAcquiredDisposedCode>
</transactionAmounts>
<exerciseDate>
<value>2003-12-02</value>
</exerciseDate>
<expirationDate>
<value>2013-12-02</value>
</expirationDate>
<underlyingSecurity>
<underlyingSecurityTitle>
<value>Common</value>
</underlyingSecurityTitle>
<underlyingSecurityShares>
<value>20000</value>
</underlyingSecurityShares>
</underlyingSecurity>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>20000</value>
</sharesOwnedFollowingTransaction>
</postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value>
</directOrIndirectOwnership>
<natureOfOwnership>
<value></value>
</natureOfOwnership>
</ownershipNature>
</derivativeTransaction>
<derivativeTransaction>
<securityTitle>
<value>Stock Option</value>
</securityTitle>
<conversionOrExercisePrice>
<value>1.75</value>
</conversionOrExercisePrice>
<transactionDate>
<value>2003-06-11</value>
</transactionDate>
<deemedExecutionDate>
</deemedExecutionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>A</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved>
</transactionCoding>
<transactionTimeliness>
<value></value>
</transactionTimeliness>
<transactionAmounts>
<transactionShares>
<value>40000</value>
</transactionShares>
<transactionPricePerShare>
<value>0</value>
</transactionPricePerShare>
<transactionAcquiredDisposedCode>
<value>A</value>
</transactionAcquiredDisposedCode>
</transactionAmounts>
<exerciseDate>
<value>2003-06-11</value>
</exerciseDate>
<expirationDate>
<value>2013-06-11</value>
</expirationDate>
<underlyingSecurity>
<underlyingSecurityTitle>
<value>Common</value>
</underlyingSecurityTitle>
<underlyingSecurityShares>
<value>40000</value>
</underlyingSecurityShares>
</underlyingSecurity>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>40000</value>
</sharesOwnedFollowingTransaction>
</postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value>
</directOrIndirectOwnership>
<natureOfOwnership>
<value></value>
</natureOfOwnership>
</ownershipNature>
</derivativeTransaction>
<derivativeTransaction>
<securityTitle>
<value>Stock Option</value>
</securityTitle>
<conversionOrExercisePrice>
<value>2.90</value>
</conversionOrExercisePrice>
<transactionDate>
<value>2002-03-13</value>
</transactionDate>
<deemedExecutionDate>
</deemedExecutionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>A</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved>
</transactionCoding>
<transactionTimeliness>
<value></value>
</transactionTimeliness>
<transactionAmounts>
<transactionShares>
<value>50000</value>
</transactionShares>
<transactionPricePerShare>
<value>0</value>
</transactionPricePerShare>
<transactionAcquiredDisposedCode>
<value>A</value>
</transactionAcquiredDisposedCode>
</transactionAmounts>
<exerciseDate>
<value>2002-03-13</value>
</exerciseDate>
<expirationDate>
<value>2012-03-13</value>
</expirationDate>
<underlyingSecurity>
<underlyingSecurityTitle>
<value>Common</value>
</underlyingSecurityTitle>
<underlyingSecurityShares>
<value>50000</value>
</underlyingSecurityShares>
</underlyingSecurity>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>50000</value>
</sharesOwnedFollowingTransaction>
</postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value>
</directOrIndirectOwnership>
<natureOfOwnership>
<value></value>
</natureOfOwnership>
</ownershipNature>
</derivativeTransaction>
<derivativeTransaction>
<securityTitle>
<value>Stock Option</value>
</securityTitle>
<conversionOrExercisePrice>
<value>1.965</value>
</conversionOrExercisePrice>
<transactionDate>
<value>2001-03-14</value>
</transactionDate>
<deemedExecutionDate>
</deemedExecutionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>A</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved>
</transactionCoding>
<transactionTimeliness>
<value></value>
</transactionTimeliness>
<transactionAmounts>
<transactionShares>
<value>20000</value>
</transactionShares>
<transactionPricePerShare>
<value>0</value>
</transactionPricePerShare>
<transactionAcquiredDisposedCode>
<value>A</value>
</transactionAcquiredDisposedCode>
</transactionAmounts>
<exerciseDate>
<value>2001-03-14</value>
</exerciseDate>
<expirationDate>
<value>2011-03-14</value>
</expirationDate>
<underlyingSecurity>
<underlyingSecurityTitle>
<value>Common</value>
</underlyingSecurityTitle>
<underlyingSecurityShares>
<value>20000</value>
</underlyingSecurityShares>
</underlyingSecurity>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>20000</value>
</sharesOwnedFollowingTransaction>
</postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value>
</directOrIndirectOwnership>
<natureOfOwnership>
<value></value>
</natureOfOwnership>
</ownershipNature>
</derivativeTransaction>
<derivativeTransaction>
<securityTitle>
<value>Stock Option</value>
</securityTitle>
<conversionOrExercisePrice>
<value>2.50</value>
</conversionOrExercisePrice>
<transactionDate>
<value>2000-02-10</value>
</transactionDate>
<deemedExecutionDate>
</deemedExecutionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>A</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved>
</transactionCoding>
<transactionTimeliness>
<value></value>
</transactionTimeliness>
<transactionAmounts>
<transactionShares>
<value>20000</value>
</transactionShares>
<transactionPricePerShare>
<value>0</value>
</transactionPricePerShare>
<transactionAcquiredDisposedCode>
<value>A</value>
</transactionAcquiredDisposedCode>
</transactionAmounts>
<exerciseDate>
<value>2000-02-10</value>
</exerciseDate>
<expirationDate>
<value>2010-02-20</value>
</expirationDate>
<underlyingSecurity>
<underlyingSecurityTitle>
<value>Common</value>
</underlyingSecurityTitle>
<underlyingSecurityShares>
<value>20000</value>
</underlyingSecurityShares>
</underlyingSecurity>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>20000</value>
</sharesOwnedFollowingTransaction>
</postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value>
</directOrIndirectOwnership>
<natureOfOwnership>
<value></value>
</natureOfOwnership>
</ownershipNature>
</derivativeTransaction>
<derivativeTransaction>
<securityTitle>
<value>Stock Option</value>
</securityTitle>
<conversionOrExercisePrice>
<value>0.90</value>
</conversionOrExercisePrice>
<transactionDate>
<value>1999-06-14</value>
</transactionDate>
<deemedExecutionDate>
</deemedExecutionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>A</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved>
</transactionCoding>
<transactionTimeliness>
<value></value>
</transactionTimeliness>
<transactionAmounts>
<transactionShares>
<value>20000</value>
</transactionShares>
<transactionPricePerShare>
<value>0</value>
</transactionPricePerShare>
<transactionAcquiredDisposedCode>
<value>A</value>
</transactionAcquiredDisposedCode>
</transactionAmounts>
<exerciseDate>
<value>1999-06-14</value>
</exerciseDate>
<expirationDate>
<value>2009-06-14</value>
</expirationDate>
<underlyingSecurity>
<underlyingSecurityTitle>
<value>Common</value>
</underlyingSecurityTitle>
<underlyingSecurityShares>
<value>20000</value>
</underlyingSecurityShares>
</underlyingSecurity>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>20000</value>
</sharesOwnedFollowingTransaction>
</postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value>
</directOrIndirectOwnership>
<natureOfOwnership>
<value></value>
</natureOfOwnership>
</ownershipNature>
</derivativeTransaction>
<derivativeTransaction>
<securityTitle>
<value>Stock Option</value>
</securityTitle>
<conversionOrExercisePrice>
<value>2.00</value>
</conversionOrExercisePrice>
<transactionDate>
<value>1998-06-05</value>
</transactionDate>
<deemedExecutionDate>
</deemedExecutionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>A</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved>
</transactionCoding>
<transactionTimeliness>
<value></value>
</transactionTimeliness>
<transactionAmounts>
<transactionShares>
<value>7500</value>
</transactionShares>
<transactionPricePerShare>
<value>0</value>
</transactionPricePerShare>
<transactionAcquiredDisposedCode>
<value>A</value>
</transactionAcquiredDisposedCode>
</transactionAmounts>
<exerciseDate>
<value>1998-06-05</value>
</exerciseDate>
<expirationDate>
<value>2008-06-05</value>
</expirationDate>
<underlyingSecurity>
<underlyingSecurityTitle>
<value>Common</value>
</underlyingSecurityTitle>
<underlyingSecurityShares>
<value>7500</value>
</underlyingSecurityShares>
</underlyingSecurity>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>7500</value>
</sharesOwnedFollowingTransaction>
</postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value>
</directOrIndirectOwnership>
<natureOfOwnership>
<value></value>
</natureOfOwnership>
</ownershipNature>
</derivativeTransaction>
<derivativeTransaction>
<securityTitle>
<value>Stock Option</value>
</securityTitle>
<conversionOrExercisePrice>
<value>4.625</value>
</conversionOrExercisePrice>
<transactionDate>
<value>1997-02-06</value>
</transactionDate>
<deemedExecutionDate>
</deemedExecutionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>A</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved>
</transactionCoding>
<transactionTimeliness>
<value></value>
</transactionTimeliness>
<transactionAmounts>
<transactionShares>
<value>10000</value>
</transactionShares>
<transactionPricePerShare>
<value>0</value>
</transactionPricePerShare>
<transactionAcquiredDisposedCode>
<value>A</value>
</transactionAcquiredDisposedCode>
</transactionAmounts>
<exerciseDate>
<value>1997-02-06</value>
</exerciseDate>
<expirationDate>
<value>2007-02-06</value>
</expirationDate>
<underlyingSecurity>
<underlyingSecurityTitle>
<value>Common</value>
</underlyingSecurityTitle>
<underlyingSecurityShares>
<value>10000</value>
</underlyingSecurityShares>
</underlyingSecurity>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>10000</value>
</sharesOwnedFollowingTransaction>
</postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value>
</directOrIndirectOwnership>
<natureOfOwnership>
<value></value>
</natureOfOwnership>
</ownershipNature>
</derivativeTransaction>
<derivativeTransaction>
<securityTitle>
<value>Stock Option</value>
</securityTitle>
<conversionOrExercisePrice>
<value>6.82</value>
</conversionOrExercisePrice>
<transactionDate>
<value>1995-12-26</value>
</transactionDate>
<deemedExecutionDate>
</deemedExecutionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>A</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved>
</transactionCoding>
<transactionTimeliness>
<value></value>
</transactionTimeliness>
<transactionAmounts>
<transactionShares>
<value>5750</value>
</transactionShares>
<transactionPricePerShare>
<value>0</value>
</transactionPricePerShare>
<transactionAcquiredDisposedCode>
<value>A</value>
</transactionAcquiredDisposedCode>
</transactionAmounts>
<exerciseDate>
<value>1995-12-26</value>
</exerciseDate>
<expirationDate>
<value>2005-12-26</value>
</expirationDate>
<underlyingSecurity>
<underlyingSecurityTitle>
<value>Common</value>
</underlyingSecurityTitle>
<underlyingSecurityShares>
<value>5750</value>
</underlyingSecurityShares>
</underlyingSecurity>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>5750</value>
</sharesOwnedFollowingTransaction>
</postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value>
</directOrIndirectOwnership>
<natureOfOwnership>
<value></value>
</natureOfOwnership>
</ownershipNature>
</derivativeTransaction>
</derivativeTable>
<remarks></remarks>
<ownerSignature>
<signatureName>Charles W. Grinnell</signatureName>
<signatureDate>2004-01-16</signatureDate>
</ownerSignature>
</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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