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| ·   | All      eligible ARS must remain      in my UBS account listed below until I exercise my Rights to sell      my Eligible ARS to UBS or they are redeemed by the issuer or purchased or      sold on my behalf by UBS; |
|--------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ·   | I      will instruct my UBS Financial Advisor or Branch Manager if and when I      want to exercise my Rights and sell my Eligible ARS to UBS during the      period of June 30, 2010, through July 2,2012; |
|--------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ·   | The      acceptance of UBS’s offer constitutes consent (to the extent legally      required) for UBS, acting as principal, to purchase my Eligible ARS or to      sell them on my behalf at any time in its sole discretion and without      other prior notice to me, from the date that I accept this offer through      July 2, 2012; |
|--------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ·   | If      UBS purchases, sells or otherwise disposes of my Eligible ARS, it will      deposit the par value in my account within one business day of settlement      of the transaction; |
|--------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ·   | I      release UBS and its employees/agents from all claims except claims for      consequential damages directly or indirectly relating to its marketing and      sale of ARS and expressly agree that I will not seek any damages or costs      (punitive damages, attorney fees, etc.) other than consequential      damages.  I also will not serve as a class representative or      receive benefits under any class action settlement or investor      fund; |
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| ·   | If      the account named below is in the name of a corporation, partnership,      trust or other equity, I represent and warrant that I have the power and      authority to accept this offer on behalf of that  entity. |
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| Clean      Diesel Technologies, Inc.   | Please      complete and sign this form.      |
|----------------------------------------|-----------------------------------------------|
| Attn:  Ann      Ruple        | We      must receive it by November 14, 2008. |
| 300      Atlantic Street               |                                          |   |
| Suite      702                         | Mail                                          | UBS      Financial Services, Inc. |
| Stamford      CT  06901-3522 |                                          | ATTN:  ARS      Group |
|                                   |                                          | 1000      Harbor Boulevard |
|                                   |                                          | Weehawken,      NJ  07086 |
|                                   |                                          |   |
|                                   | Fax                                           | +1-201-442-7766 |

| Account      Number:  CP 06577 |                                                                   |   |   |    |
|------------------------------------------|------------------------------------------------------------------------|--------|--------|---------|
|                                     |                                                                   |   |   |    |
| Account      Owner Signature             | /s/  Ann B.      Ruple    Vice President |   | Date   | 11/5/08 |
|                                     |                                                                   |   |   |    |
| Additional      Party Signature          | /s/  C. W.      Grinnell   Vice President     |   | Date   | 11/5/08 |
|                                     |                                                                   |   |   |    |
| Daytime      Telephone Number            | (203) 327-7050                                                         |   |   |    |

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