Investor Presentaiton

Specified Financial Measures Reconciliation of non-GAAP financial measures Pro forma adjusted EBITDA reconciliation to the nearest GAAP measure, Net Income, for the Corporation and STLLC: 430 Presentation of Pro Forma Financial Information The pro forma financial information referred to in this presentation was prepared utilizing accounting policies that are consistent with those disclosed in the unaudited consolidated financial statements of Gibson as at and for the three and nine months ended September 30, 2023, and the audited consolidated financial statements for the year ended December 31, 2022 and was prepared in accordance with recognition and measurement principles of IFRS. The pro forma financial information has been derived from, and should be read in conjunction with: (i) the unaudited condensed consolidated financial statements of Gibson as at and for the three and nine months ended September 30, 2023, (ii) the audited consolidated financial statements of Gibson for the year ended December 31, 2022, (iii) the audited financial statements of STLLC as at and for the year ended December 31, 2022, (iv) the unaudited financial statements of STLLC as at and for the three months ended March 31, 2023, and (v) financial information and operational results of STLLC for the period following March 31, 2023 and prior to the closing of the acquisition, as applicable. See "Forward- Looking Statement Notice". Gibson has not independently verified the financial statements of STLLC that were used to prepare certain of the pro forma financial information included in this presentation and the pro forma financial information included in this presentation is not intended to be indicative of the results that would actually have occurred, or the results expected in future periods, had the events reflected in this presentation occurred on the dates indicated. The pro forma financial information contained in this presentation is included for informational purposes only and undue reliance should not be placed on such pro forma financial information. The unaudited pro forma condensed consolidated financial information contained in this presentation is presented for illustrative purposes only as of its respective dates and may not be indicative of the financial condition, results of operations or cash flows of Gibson following completion of the acquisition or had the acquisition been completed as of beginning of the respective periods presented. The unaudited pro forma condensed consolidated financial information was derived from the respective historical financial statements of Gibson and STLLC, the financial information and operational results of STLLC for the period following March 31, 2023 and prior to the closing of the acquisition, and certain adjustments and assumptions were made to give effect to the acquisition, as applicable. The information upon which such adjustments and assumptions were made was preliminary and adjustments and assumptions of this nature are difficult to make with complete accuracy. Moreover, the unaudited pro forma condensed consolidated financial information does not include, among other things, estimated synergies or adjustments related to restructuring or integration activities in connection with the acquisition, or future acquisitions or disposals not yet known or probable. Additionally, the unaudited pro forma condensed consolidated financial information may not reflect all of the costs that are expected to be incurred by STLLC and Gibson in connection with the acquisition. Accordingly, Gibson's assets, results of operations and financial condition following the acquisition may differ significantly from those indicated in the unaudited pro forma financial information and financial information and operational results of STLLC for periods following March 31, 2023 and prior to the closing of the acquisition may not be consistent with past financial and operational results for similar periods in respect of STLLC. The audited financial statements of STLLC as of and for the years ended December 31, 2022 and 2021 and the unaudited financial statements of STLLC for the three months ended March 31, 2023 are each included in Gibson's Business Acquisition Report dated October 6, 2023, available on SEDAR+ at sedarplus.ca (CAD$ in thousands) Net income Income tax expense Depreciation, amortization and impairment Finance costs, net For the twelve months ended September 30, 2023 Gibson STLLC(1) Other(2) 224,802 114,869 70,108 907 Pro forma 339,671 71,015 125,622 14,379 98,184. Unrealized (gain)/loss on derivative financial instruments (9,132) 140,001 98,184 (9,132) Corporate unrealized (gain)/loss on derivative financial instrument 430 Stock based compensation 20,460 Acquisition and integration costs 19,959 Adjustments to share of profit from equity accounted investees 5,693 Corporate foreign exchange (gain)/loss and other Adjusted EBITDA 1,355 557,481 20,460 130,156 16,744 16,744 19,959 5,693 18,099 704,381 GIBSON ENERGY INVESTOR PRESENTATION Pro forma distributable cash flow reconciliation to the nearest GAAP measure, cash flow from operating activities, for the Corporation and STLLC: (CAD$ in thousands) STLLC(1) For the twelve months ended December 31, 2022 Gibson Adjustments Pro forma 598,312 143,383 741,695 Cash flow from operating activities Adjustments: Changes in non-cash working capital and taxes paid Replacement capital (81,576) (4,558) (86,134) (22,241) (22,241) Cash interest expense, including capitalized interest (59,816) (74,642) (134,458) Lease payments (35,397) (35,397) Current income tax Distributable cash flow (43,074) 356,208 (848) 137,977 (9,290) (83,932) (53,212) 410,253 30 (1) Column was derived from the historical results of STLLC prior to the close of the Transaction, which was prepared in U.S. dollars; the exchange rate used to translate the U.S. dollar amounts is the average exchange rate for each month of historical results. (2) Reflects impact of add back $16.8mm for the Q2 2023 environmental remediation accrual. (3) Pro forma adjustments to reflect additional interest expense for the assumed financing structure (i.e. the Transaction is funded from the net proceeds of the Equity Offering and the bridge financing facilities) as well as additional income tax expense relating to STLLC.

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