**EXHIBIT      31.2**

**Certification      By Chief Financial Officer**

**Pursuant      To Rule 13a-14(a) and 15d-14(a) Under The Exchange Act**

| 1.   | I              have reviewed this annual report on Form 10-K of Frontier Oil              Corporation; |
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| 2.   | Based              on my knowledge, this report does not contain any untrue statement              of a              material fact or omit to state a material fact necessary to make the              statements made, in light of the circumstances under which such statements              were made, not misleading with respect to the period covered by this              report; |
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| 3.   | Based              on my knowledge, the financial statements, and other financial information              included in this report, fairly present in all material respects the              financial condition, results of operations and cash flows of the              registrant as of, and for, the periods presented in this              report; |
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| 4.   | The              registrant’s other certifying officers and I are responsible for              establishing and maintaining disclosure controls and procedures (as              defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and the internal              control over financial reporting (as defined in Exchange Act Rules              13a-15(f) and 15d-15(f)) for the registrant and              have: |
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| a)   | Designed              such disclosure controls and procedures, or caused such disclosure              controls and procedures to be designed under our supervision, to ensure              that material information relating to the registrant, including its              consolidated subsidiaries, is made known to us by others within those              entities, particularly during the period in which this report is being              prepared; |
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|   |  b) | Designed                such internal control over financial reporting, or caused such internal                control over financial reporting to be designed under our supervision,                to                provide reasonable assurance regarding reliability of financial reporting                and the preparation of financial statements for external purposes                in                accordance with generally accepted accounting                principles; |
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|   |  c) | Evaluated                the effectiveness of the registrant’s disclosure controls and procedures                and presented in this report our conclusions about the effectiveness                of                the disclosure controls and procedures, as of the end of the period                covered by this report based on such evaluation;                and |
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|   |  d) | Disclosed                in this report any change in the registrant’s internal control over                financial reporting that occurred during the registrant’s most recent                fiscal quarter (the registrant’s fourth fiscal quarter in the case of an                annual report) that has materially affected, or is reasonably likely                to                materially affect, the registrant’s internal control over financial                reporting; and |
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| 5.   | The              registrant’s other certifying officers and I have disclosed, based on our              most recent evaluation of internal control over financial reporting,              to              the registrant’s auditors and the audit committee of the registrant’s              board of directors (or persons performing the equivalent              functions): |
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| a)   | All                significant deficiencies and material weaknesses in the design or                operation of internal control over financial reporting which are                reasonably likely to adversely affect the registrant’s ability to record,                process, summarize and report financial information; and  |
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|   |  b) | Any                fraud, whether or not material, that involves management or other                employees who have a significant role in the registrant’s internal control                over financial reporting. |
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