M A N A G E M E N T ’ S R E P O R T O N I N T E R N A L C O N T R O L O V E R F I N A N C I A L R E P O R T I N G  The management of PACCAR Inc (the Company) is responsible for establishing and maintaining adequate internal  control over financial reporting. Internal control over financial reporting is a process designed to provide reasonable  assurance regarding the reliability of financial reporting and the preparation of financial statements for external  purposes in accordance with generally accepted accounting principles. Internal control over financial reporting may not prevent or detect misstatements because of its inherent  limitations. Projections of any evaluation of effectiveness to future periods are subject to the risk that controls may  become inadequate because of changes in conditions, or that the degree of compliance with the policies and  procedures may deteriorate. Management assessed the Company’s internal control over financial reporting as of December 31, 2011, based on  criteria for effective internal control over financial reporting described in Internal Control—Integrated Framework  issued by the Committee of Sponsoring Organizations of the Treadway Commission. Based on this assessment, we  concluded that the Company maintained effective internal control over financial reporting as of December 31, 2011. Ernst & Young LLP, the Independent Registered Public Accounting Firm that audited the financial statements  included in this Annual Report, has issued an attestation report on the Company’s internal control over financial  reporting. The attestation report is included on page 81. The Board of Directors and Stockholders of PACCAR Inc We have audited the accompanying consolidated balance sheets of PACCAR Inc as of December 31, 2011 and 2010,  and the related consolidated statements of income, comprehensive income, stockholders’ equity, and cash flows for  each of the three years in the period ended December 31, 2011. These financial statements are the responsibility of  the Company’s management. Our responsibility is to express an opinion on these financial statements based on our  audits. We conducted our audits in accordance with the standards of the Public Company Accounting Oversight Board  (United States). Those standards require that we plan and perform the audit to obtain reasonable assurance about  whether the financial statements are free of material misstatement. An audit includes examining, on a test basis,  evidence supporting the amounts and disclosures in the financial statements. An audit also includes assessing the  accounting principles used and significant estimates made by management, as well as evaluating the overall  financial statement presentation. We believe that our audits provide a reasonable basis for our opinion. In our opinion, the financial statements referred to above present fairly, in all material respects, the consolidated  financial position of PACCAR Inc at December 31, 2011 and 2010, and the consolidated results of its operations  and its cash flows for each of the three years in the period ended December 31, 2011, in conformity with U.S.  generally accepted accounting principles. We also have audited, in accordance with the standards of the Public Company Accounting Oversight Board  (United States), PACCAR Inc’s internal control over financial reporting as of December 31, 2011, based on criteria  established in Internal Control—Integrated Framework issued by the Committee of Sponsoring Organizations of  the Treadway Commission and our report dated February 29, 2012 expressed an unqualified opinion thereon. REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM  ON THE COM PANY’S CONSOLIDATED FINANCIAL STATEM ENTS Mark C. Pigott Chairman and Chief Executive Officer Seattle, Washington February 29, 2012