Summary of Significant Accounting Policies (Policies)	6 Months Ended
Jun. 30, 2026
Accounting Policies [Abstract]
Basis of Accounting	The unaudited condensed consolidated financial statements of the Company as of June 30, 2026 and for the three and six months ended June 30, 2026 and 2025, included herein have been prepared, without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). Certain information and disclosures normally included in the consolidated financial statements prepared in accordance with generally accepted accounting principles (“GAAP”) in the U.S. have been condensed or omitted pursuant to such rules and regulations, although the Company believes that the following disclosures are adequate to make the information presented not misleading. The preparation of the unaudited condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the unaudited condensed consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. These unaudited condensed consolidated financial statements reflect all adjustments that, in the opinion of management, are necessary to present fairly the results of operations for the interim periods presented. All adjustments are of a normal nature, unless otherwise disclosed.
Reclassifications	Reclassifications Certain amounts in the prior years’ unaudited condensed consolidated financial statements have been reclassified to conform to the current year presentation.
Cash and Cash Equivalents and Restricted Cash	Cash and Cash Equivalents and Restricted Cash Cash and cash equivalents and restricted cash include all highly liquid investments with a maturity of three months or less at the time of purchase. Cash and cash equivalents are deposited primarily in banking institutions with global operations. We have not experienced any losses in such accounts. We believe we are not exposed to any significant credit risk related to cash and cash equivalents. Restricted cash as of June 30, 2026 and December 31, 2025 represents cash that is restricted under the Department of Energy Loan Guarantee Agreement (the “DOE Loan”) because it is only available to make certain investments under the terms of the DOE Loan.
Renewable Identification Numbers ("RINs") Obligation	Renewable Identification Numbers (“RINs”) Obligation Under the Renewable Fuel Standard (“RFS”) of the Clean Air Act, certain refineries are required to comply with annual Renewable Volume Obligations (“RVOs”) established by the U.S. Environmental Protection Agency (“EPA”). The EPA sets annual RVOs for the percentage of renewable fuels that must be blended into transportation fuels consumed in the United States. Compliance is satisfied through the blending of renewable fuels, the purchase and retirement of Renewable Identification Numbers (“RINs”), or the receipt of a Small Refinery Exemption (“SRE”). A RIN is a 38-character number assigned to each physical gallon of renewable fuel produced in or imported into the United States. The Company accounts for its current-period RVO as an estimated liability measured by multiplying the net RINs obligation, based on actual production volumes, by the period-end market price of RINs. The resulting liability is recorded as a current liability and remeasured at each reporting date, with changes recognized in cost of sales. Gains and losses from the sale of RINs are also recorded in cost of sales. The RVO represents an obligation to retire RINs and cannot be settled in cash with the EPA but may be settled through the purchase of a RIN. Historically, the Company has received SREs and was not required to purchase RINs. Beginning in 2022, EPA denied the Company’s SRE petitions for multiple compliance years, which resulted in the recognition of significant RINs liabilities. Those denials were subsequently challenged and, in several instances, vacated and remanded by federal courts. In August 2025, EPA issued new hardship determinations that (i) reaffirmed prior grants of the Company’s 2018 SREs, (ii) issued new decisions for program years 2019 through 2023, and (iii) issued decisions on the Company’s 2024 petitions. Under those decisions, the Company received full or partial relief for its Shreveport and Montana refineries for program years 2019 through 2024, which reduced the number of RINs required to be retired. The EPA has not yet issued a decision on the Company’s 2025 SRE petitions. The Company has filed petitions for judicial review of certain EPA decisions relating to the 2022 through 2024 program years in which the Company received only a partial exemption. The EPA has confirmed that it does not intend to pursue enforcement actions while SRE petitions or related litigation are pending and that, if required, the Company will be afforded a reasonable period to achieve compliance. Expenses related to RFS compliance may continue to be significant. Adverse legal or regulatory developments, higher RIN prices, or a reduction or elimination of SRE availability could require the Company to purchase additional RINs, which could materially adversely affect results of operations and liquidity.
New Accounting Standards	New Accounting Standards In December 2023, the FASB issued ASU 2023-09, “Income Taxes (Topic 740): Improvements to Income Tax Disclosures”, which requires public entities, on an annual basis, to provide disclosure of specific categories in the rate reconciliation, as well as disclosure of income taxes paid disaggregated by jurisdiction. ASU 2023-09 is effective for fiscal years beginning after December 15, 2024, with early adoption permitted. The Company adopted ASU 2023-09 for the year ended December 31, 2025, and applied the new disclosure requirements prospectively to the 2025 annual period. Prior period disclosures have not been adjusted to reflect the new disclosure requirements Refer to Note 11 — “Income Taxes” for additional information. In November 2024, the FASB issued ASU 2024-03, “Income Statement – Reporting Comprehensive Income – Expense Disaggregation Disclosures.” This ASU seeks to improve the disclosures about a public business entity’s expenses by providing more detailed information about the types of expenses in commonly presented expense captions. This ASU is effective for fiscal years beginning after December 15, 2026 and interim periods within fiscal years beginning after December 15, 2027. We are currently evaluating the impact this update will have on our consolidated financial statements and footnotes. In May 2026, the FASB issued ASU 2026-02, "Environmental Credits and Environmental Credit Obligations." This ASU seeks to improve the financial accounting for and disclosure of environmental credits and environmental credit obligations. This update provides recognition, measurement, presentation, and disclosure requirements for all entities that generate, purchase, or receive environmental credits or have a regulatory compliance obligation that may be settled with environmental credits. This ASU is effective for fiscal years beginning after December 15, 2027 and interim periods within fiscal years beginning after December 15, 2028. We are currently evaluating the impact this update will have on our consolidated financial statements and footnotes.
Inventories	An actual valuation of inventory under the LIFO method can be made only at the end of each year based on the inventory levels and costs at that time. Accordingly, interim LIFO calculations are based on management’s estimates of expected year-end inventory levels and costs and are subject to the final year-end LIFO inventory valuation. In certain circumstances, the Company may decide not to replenish inventory for certain products or product lines during an interim period, in which case, the Company may record interim LIFO adjustments during that period. During the three and six months ended June 30, 2026 and 2025, the Company recorded no activity (exclusive of lower of cost or market (“LCM”) adjustments) in cost of sales in the unaudited condensed consolidated statements of operations due to the permanent liquidation of inventory layers. Costs include crude oil and other feedstocks, labor, processing costs, and refining overhead costs. Inventories are valued at the LCM value.
Fair Value Measurements	In accordance with ASC 820, the Company uses a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value. Observable inputs are from sources independent of the Company. Unobservable inputs reflect the Company’s assumptions about the factors market participants would use in valuing the asset or liability developed based upon the best information available in the circumstances. These tiers include the following: •Level 1 — inputs include observable unadjusted quoted prices in active markets for identical assets or liabilities •Level 2 — inputs include other than quoted prices in active markets that are either directly or indirectly observable •Level 3 — inputs include unobservable inputs in which little or no market data exists, therefore requiring an entity to develop its own assumptions In determining fair value, the Company uses various valuation techniques and prioritizes the use of observable inputs. The availability of observable inputs varies from instrument to instrument and depends on a variety of factors including the type of instrument, whether the instrument is actively traded and other characteristics particular to the instrument. For many financial instruments, pricing inputs are readily observable in the market, the valuation methodology used is widely accepted by market participants and the valuation does not require significant management judgment. For other financial instruments, pricing inputs are less observable in the marketplace and may require management judgment. There have been no material changes in our derivative assets and liabilities measurements, pension assets, liability awards, and precious metals obligations from those previously disclosed in our Annual Report on Form 10-K for the fiscal year ended December 31, 2025. Certain non-financial assets and liabilities are measured at fair value on a nonrecurring basis and are subject to fair value adjustments in certain circumstances. The carrying value of cash, cash equivalents and restricted cash are each considered to be representative of their fair value.
Segment Reporting	The Company determines its reportable segments based on how the business is managed internally for the products sold to customers, including how results are reviewed and resources are allocated. Effective January 1, 2026, the Company reorganized its business segments as a result of a change in how our chief operating decision maker (“CODM”) allocates resources, makes operating decisions, and assesses the performance of its business. As a result, as of January 1, 2026, the Company’s operations are managed by the CODM using the following reportable segments: •Specialty Products and Solutions. The Specialty Products and Solutions segment consists of our customer-focused solutions and formulations businesses, covering multiple specialty product lines, anchored by our unique integrated complex in Northwest Louisiana. In this segment, we manufacture and market a wide variety of solvents, waxes, customized lubricating oils, white oils, petrolatums, gels, esters, and other products. Our specialty products are sold to domestic and international customers who purchase them primarily as raw material components for consumer-facing and industrial products. •Montana/Renewables. The Montana/Renewables segment is composed of our Montana Renewables facility and our Great Falls specialty asphalt facility. At our Montana Renewables facility, we process a variety of geographically advantaged renewable feedstocks into renewable diesel, sustainable aviation fuel, renewable hydrogen, renewable natural gas, renewable propane, and renewable naphtha that are distributed into renewable markets in the western half of North America. At our Montana specialty asphalt facility, we process Canadian crude oil into conventional gasoline, diesel, jet fuel and specialty grades of asphalt, with production sized to serve local markets. •Performance Brands. The Performance Brands segment includes our fast-growing portfolio of high-quality, high-performing brands. In this segment, we blend, package, and market high performance products through our Royal Purple, Bel-Ray, and TruFuel brands. The accounting policies of the reporting segments are the same as those described in the summary of significant accounting policies as disclosed in Note 2 — “Summary of Significant Accounting Policies,” except that the disaggregated financial results for the reporting segments have been prepared using a management approach, which is consistent with the basis and manner in which management internally disaggregates financial information for the purposes of assisting internal operating decisions. The Company accounts for inter-segment sales and transfers using market-based transfer pricing. The Company will periodically refine its expense allocation methodology for its segment reporting as more specific information becomes available and the industry or market changes. The CODM uses Adjusted EBITDA (a non-GAAP financial measure) to evaluate performance and allocate resources to each segment, primarily through periodic budgeting and segment performance reviews. The Company defines Adjusted EBITDA for any period as EBITDA adjusted for (a) impairment; (b) unrealized gains and losses from mark-to-market accounting for hedging activities; (c) realized gains and losses under derivative instruments excluded from the determination of net income (loss); (d) non-cash equity-based compensation expense and other non-cash items (excluding items such as accruals of cash expenses in a future period or amortization of a prepaid cash expense) that were deducted in computing net income (loss); (e) debt refinancing fees, extinguishment costs, premiums and penalties; (f) any net gain or loss realized in connection with an asset sale that was deducted in computing net income (loss); (g) amortization of turnaround costs; (h) LCM inventory adjustments; (i) the impact of liquidation of inventory layers calculated using the LIFO method; (j) RINs mark-to-market adjustments; (k) RINs incurrence expense; and (l) all extraordinary, unusual or non-recurring items of gain or loss, or revenue or expense.
Unrestricted Subsidiaries	As defined in the indentures governing the Company’s outstanding senior notes, an unrestricted subsidiary means MRHL, MRL and any other subsidiary of the Company, other than Calumet Finance Corp., that is designated by the governing body of the General Partner as an unrestricted subsidiary, but only to the extent that such subsidiary: •has no indebtedness other than non-recourse debt owing to any person other than the Company or any of its restricted subsidiaries, except to the extent permitted by the indentures of the senior notes; •is not party to any agreement, contract, arrangement or understanding with the Company or any restricted subsidiary of the Company unless the terms of any such agreement, contract, arrangement or other understanding are no less favorable to the Company or such restricted subsidiary than those that might be obtained at the time from persons who are not affiliates of the Company, except to the extent permitted by the indentures of the senior notes; •is a person with respect to which neither the Company nor any of its restricted subsidiaries has any direct or indirect obligation (a) to subscribe for additional equity interests or (b) to maintain or preserve such person’s financial condition or to cause such person to achieve any specified levels of operating results, except to the extent permitted by the indentures of the senior notes; and •has not guaranteed or otherwise directly or indirectly provided credit support for any indebtedness of the Company or any of its restricted subsidiaries.

Summary of Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2026

The unaudited condensed consolidated financial statements of the Company as of June 30, 2026 and for the three and six months ended June 30, 2026 and 2025, included herein have been prepared, without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). Certain information and disclosures normally included in the consolidated financial statements prepared in accordance with generally accepted accounting principles (“GAAP”) in the U.S. have been condensed or omitted pursuant to such rules and regulations, although the Company believes that the following disclosures are adequate to make the information presented not misleading. The preparation of the unaudited condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the unaudited condensed consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. These unaudited condensed consolidated financial statements reflect all adjustments that, in the opinion of management, are necessary to present fairly the results of operations for the interim periods presented. All adjustments are of a normal nature, unless otherwise disclosed.

Reclassifications

Certain amounts in the prior years’ unaudited condensed consolidated financial statements have been reclassified to conform to the current year presentation.

Cash and Cash Equivalents and Restricted Cash

Cash and cash equivalents and restricted cash include all highly liquid investments with a maturity of three months or less at the time of purchase. Cash and cash equivalents are deposited primarily in banking institutions with global operations. We have not experienced any losses in such accounts. We believe we are not exposed to any significant credit risk related to cash and cash equivalents.

Restricted cash as of June 30, 2026 and December 31, 2025 represents cash that is restricted under the Department of Energy Loan Guarantee Agreement (the “DOE Loan”) because it is only available to make certain investments under the terms of the DOE Loan.

Renewable Identification Numbers ("RINs") Obligation

Renewable Identification Numbers (“RINs”) Obligation

Under the Renewable Fuel Standard (“RFS”) of the Clean Air Act, certain refineries are required to comply with annual Renewable Volume Obligations (“RVOs”) established by the U.S. Environmental Protection Agency (“EPA”). The EPA sets annual RVOs for the percentage of renewable fuels that must be blended into transportation fuels consumed in the United States. Compliance is satisfied through the blending of renewable fuels, the purchase and retirement of Renewable Identification Numbers (“RINs”), or the receipt of a Small Refinery Exemption (“SRE”). A RIN is a 38-character number assigned to each physical gallon of renewable fuel produced in or imported into the United States.

The Company accounts for its current-period RVO as an estimated liability measured by multiplying the net RINs obligation, based on actual production volumes, by the period-end market price of RINs. The resulting liability is recorded as a current liability and remeasured at each reporting date, with changes recognized in cost of sales. Gains and losses from the sale of RINs are also recorded in cost of sales. The RVO represents an obligation to retire RINs and cannot be settled in cash with the EPA but may be settled through the purchase of a RIN.

Historically, the Company has received SREs and was not required to purchase RINs. Beginning in 2022, EPA denied the Company’s SRE petitions for multiple compliance years, which resulted in the recognition of significant RINs liabilities. Those denials were subsequently challenged and, in several instances, vacated and remanded by federal courts.

In August 2025, EPA issued new hardship determinations that (i) reaffirmed prior grants of the Company’s 2018 SREs, (ii) issued new decisions for program years 2019 through 2023, and (iii) issued decisions on the Company’s 2024 petitions. Under those decisions, the Company received full or partial relief for its Shreveport and Montana refineries for program years 2019 through 2024, which reduced the number of RINs required to be retired. The EPA has not yet issued a decision on the Company’s 2025 SRE petitions.

The Company has filed petitions for judicial review of certain EPA decisions relating to the 2022 through 2024 program years in which the Company received only a partial exemption. The EPA has confirmed that it does not intend to pursue enforcement actions while SRE petitions or related litigation are pending and that, if required, the Company will be afforded a reasonable period to achieve compliance.

Expenses related to RFS compliance may continue to be significant. Adverse legal or regulatory developments, higher RIN prices, or a reduction or elimination of SRE availability could require the Company to purchase additional RINs, which could materially adversely affect results of operations and liquidity.

New Accounting Standards

In December 2023, the FASB issued ASU 2023-09, “Income Taxes (Topic 740): Improvements to Income Tax Disclosures”, which requires public entities, on an annual basis, to provide disclosure of specific categories in the rate reconciliation, as well as disclosure of income taxes paid disaggregated by jurisdiction. ASU 2023-09 is effective for fiscal years beginning after December 15, 2024, with early adoption permitted. The Company adopted ASU 2023-09 for the year ended December 31, 2025, and applied the new disclosure requirements prospectively to the 2025 annual period. Prior period disclosures have not been adjusted to reflect the new disclosure requirements Refer to Note 11 — “Income Taxes” for additional information.

In November 2024, the FASB issued ASU 2024-03, “Income Statement – Reporting Comprehensive Income – Expense Disaggregation Disclosures.” This ASU seeks to improve the disclosures about a public business entity’s expenses by providing more detailed information about the types of expenses in commonly presented expense captions. This ASU is effective for fiscal years beginning after December 15, 2026 and interim periods within fiscal years beginning after December 15, 2027. We are currently evaluating the impact this update will have on our consolidated financial statements and footnotes.

In May 2026, the FASB issued ASU 2026-02, "Environmental Credits and Environmental Credit Obligations." This ASU seeks to improve the financial accounting for and disclosure of environmental credits and environmental credit obligations. This update provides recognition, measurement, presentation, and disclosure requirements for all entities that generate, purchase, or receive environmental credits or have a regulatory compliance obligation that may be settled with environmental credits. This ASU is effective for fiscal years beginning after December 15, 2027 and interim periods within fiscal years beginning after December 15, 2028. We are currently evaluating the impact this update will have on our consolidated financial statements and footnotes.

Inventories

An actual valuation of inventory under the LIFO method can be made only at the end of each year based on the inventory levels and costs at that time. Accordingly, interim LIFO calculations are based on management’s estimates of expected year-end inventory levels and costs and are subject to the final year-end LIFO inventory valuation. In certain circumstances, the Company may decide not to replenish inventory for certain products or product lines during an interim period, in which case, the Company may record interim LIFO adjustments during that period. During the three and six months ended June 30, 2026 and 2025, the Company recorded no activity (exclusive of lower of cost or market (“LCM”) adjustments) in cost of sales in the unaudited condensed consolidated statements of operations due to the permanent liquidation of inventory layers. Costs include crude oil and other feedstocks, labor, processing costs, and refining overhead costs. Inventories are valued at the LCM value.

Fair Value Measurements

In accordance with ASC 820, the Company uses a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value. Observable inputs are from sources independent of the Company. Unobservable inputs reflect the Company’s assumptions about the factors market participants would use in valuing the asset or liability developed based upon the best information available in the circumstances. These tiers include the following:

•Level 1 — inputs include observable unadjusted quoted prices in active markets for identical assets or liabilities

•Level 2 — inputs include other than quoted prices in active markets that are either directly or indirectly observable

•Level 3 — inputs include unobservable inputs in which little or no market data exists, therefore requiring an entity to develop its own assumptions

In determining fair value, the Company uses various valuation techniques and prioritizes the use of observable inputs. The availability of observable inputs varies from instrument to instrument and depends on a variety of factors including the type of instrument, whether the instrument is actively traded and other characteristics particular to the instrument. For many financial instruments, pricing inputs are readily observable in the market, the valuation methodology used is widely accepted by market participants and the valuation does not require significant management judgment. For other financial instruments, pricing inputs are less observable in the marketplace and may require management judgment.

There have been no material changes in our derivative assets and liabilities measurements, pension assets, liability awards, and precious metals obligations from those previously disclosed in our Annual Report on Form 10-K for the fiscal year ended December 31, 2025.

Certain non-financial assets and liabilities are measured at fair value on a nonrecurring basis and are subject to fair value adjustments in certain circumstances.

The carrying value of cash, cash equivalents and restricted cash are each considered to be representative of their fair value.

Segment Reporting

The Company determines its reportable segments based on how the business is managed internally for the products sold to customers, including how results are reviewed and resources are allocated. Effective January 1, 2026, the Company reorganized its business segments as a result of a change in how our chief operating decision maker (“CODM”) allocates resources, makes operating decisions, and assesses the performance of its business. As a result, as of January 1, 2026, the Company’s operations are managed by the CODM using the following reportable segments:

•Specialty Products and Solutions. The Specialty Products and Solutions segment consists of our customer-focused solutions and formulations businesses, covering multiple specialty product lines, anchored by our unique integrated complex in Northwest Louisiana. In this segment, we manufacture and market a wide variety of solvents, waxes, customized lubricating oils, white oils, petrolatums, gels, esters, and other products. Our specialty products are sold to domestic and international customers who purchase them primarily as raw material components for consumer-facing and industrial products.

•Montana/Renewables. The Montana/Renewables segment is composed of our Montana Renewables facility and our Great Falls specialty asphalt facility. At our Montana Renewables facility, we process a variety of geographically advantaged renewable feedstocks into renewable diesel, sustainable aviation fuel, renewable hydrogen, renewable natural gas, renewable propane, and renewable naphtha that are distributed into renewable markets in the western half of North America. At our Montana specialty asphalt facility, we process Canadian crude oil into conventional gasoline, diesel, jet fuel and specialty grades of asphalt, with production sized to serve local markets.

•Performance Brands. The Performance Brands segment includes our fast-growing portfolio of high-quality, high-performing brands. In this segment, we blend, package, and market high performance products through our Royal Purple, Bel-Ray, and TruFuel brands.

The accounting policies of the reporting segments are the same as those described in the summary of significant accounting policies as disclosed in Note 2 — “Summary of Significant Accounting Policies,” except that the disaggregated financial results for the reporting segments have been prepared using a management approach, which is consistent with the basis and manner in which management internally disaggregates financial information for the purposes of assisting internal operating decisions. The Company accounts for inter-segment sales and transfers using market-based transfer pricing. The Company will periodically refine its expense allocation methodology for its segment reporting as more specific information becomes available and the industry or market changes. The CODM uses Adjusted EBITDA (a non-GAAP financial measure) to evaluate performance and allocate resources to each segment, primarily through periodic budgeting and segment performance reviews. The Company defines Adjusted EBITDA for any period as EBITDA adjusted for (a) impairment; (b) unrealized gains and losses from mark-to-market accounting for hedging activities; (c) realized gains and losses under derivative instruments excluded from the determination of net income (loss); (d) non-cash equity-based compensation expense and other non-cash items (excluding items such as accruals of cash expenses in a future period or amortization of a prepaid cash expense) that were deducted in computing net income (loss); (e) debt refinancing fees, extinguishment costs, premiums and penalties; (f) any net gain or loss realized in connection with an asset sale that was deducted in computing net income (loss); (g) amortization of turnaround costs; (h) LCM inventory adjustments; (i) the impact of liquidation of inventory layers calculated using the LIFO method; (j) RINs mark-to-market adjustments; (k) RINs incurrence expense; and (l) all extraordinary, unusual or non-recurring items of gain or loss, or revenue or expense.

Unrestricted Subsidiaries

As defined in the indentures governing the Company’s outstanding senior notes, an unrestricted subsidiary means MRHL, MRL and any other subsidiary of the Company, other than Calumet Finance Corp., that is designated by the governing body of the General Partner as an unrestricted subsidiary, but only to the extent that such subsidiary:

•has no indebtedness other than non-recourse debt owing to any person other than the Company or any of its restricted subsidiaries, except to the extent permitted by the indentures of the senior notes;

•is not party to any agreement, contract, arrangement or understanding with the Company or any restricted subsidiary of the Company unless the terms of any such agreement, contract, arrangement or other understanding are no less favorable to the Company or such restricted subsidiary than those that might be obtained at the time from persons who are not affiliates of the Company, except to the extent permitted by the indentures of the senior notes;

•is a person with respect to which neither the Company nor any of its restricted subsidiaries has any direct or indirect obligation (a) to subscribe for additional equity interests or (b) to maintain or preserve such person’s financial condition or to cause such person to achieve any specified levels of operating results, except to the extent permitted by the indentures of the senior notes; and

•has not guaranteed or otherwise directly or indirectly provided credit support for any indebtedness of the Company or any of its restricted subsidiaries.