Petro-canada 40-F/A 2007 FY Annual report (Canada) (amended)

Exhibit 99.11

CERTIFICATION PURSUANT TO 18 U.S.C. SECTION 1350, AS ADOPTED

PURSUANT TO SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with this Amendment No. 1 to the annual report of Petro-Canada (the "Company") on Form 40-F for the fiscal year ending December 31, 2006 as filed with the Securities and Exchange Commission on March 29^th, 2007 (the "Report"), I, E. F. H. Roberts, Executive Vice-President and Chief Financial Officer of the Company, certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that:

1. the Report fully complies with the requirements of section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

2. the information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

Date:   October 1, 2007 /s/ E.F.H. Roberts E. F. H. Roberts Executive Vice-President and Chief Financial Officer