**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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| 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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