UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported) November 21, 2013

Capital Auto Receivables Asset Trust 2013-4

(Issuing Entity with respect to Securities)

Capital Auto Receivables LLC

(Depositor with respect to Securities)

Registrant’s Telephone Number, including area code: (313) 656-5500

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Item 1.01 and 8.01. Entry into a Material Definitive Agreement and Other Events

Capital Auto Receivables LLC (“Capital Auto”) has registered an issuance of $18,052,591,000 in principal amount of asset backed notes on Form S-3 (Registration File No. 333-171684) under the Securities Act of 1933, as amended (the “Act”), filed on January 13, 2011, as amended by Pre-Effective Amendment No. 1 on December 6, 2011 (as amended, the “Registration Statement”).

On November 21, 2013, Capital Auto and Ally Financial Inc. entered into an Underwriting Agreement with Merrill Lynch, Piece, Fenner & Smith Incorporated, Credit Suisse Securities (USA) LLC and Deutsche Bank Securities Inc., as representatives of the several underwriters named therein (collectively, the “Underwriters”), for the issuance and sale of certain asset backed notes of Capital Auto Receivables Asset Trust 2013-4 (the “Issuing Entity”) in the following classes: (i) the Class A-1 Asset Backed Notes (the “Class A-1 Notes”), (ii) the Class A-2 Asset Backed Notes (the “Class A-2 Notes”), (iii) the Class A-3 Asset Backed Notes (the “Class A-3 Notes”), (iv) the Class A-4 Asset Backed Notes (the “Class A-4 Notes” and collectively with the Class A-1 Notes, the Class A-2 Notes and the Class A-3 Notes, the “Class A Notes”), (v) the Class B Asset Backed Notes (the “Class B Notes”), (vi) the Class C Asset Backed Notes (the “Class C Notes”) and (vii) the Class D Asset Backed Notes (the “Class D Notes” and collectively with the Class A Notes, the Class B Notes and the Class C Notes, the “Offered Notes”). The Offered Notes have an aggregate principal balance of $1,000,040,000. The Class E Asset Backed Notes (the “Class E Notes” and collectively with the Offered Notes, the “Notes”) will also be issued by the Issuing Entity. Only the Offered Notes have been registered pursuant to the Act under the Registration Statement. The Class E Notes and the Certificates will initially be held by the Depositor. It is expected that the Notes will be issued on or about November 27, 2013 (the “Closing Date”).

This Current Report on Form 8-K is being filed to satisfy an undertaking to file copies of certain agreements executed in connection with the issuance of the Offered Notes, the forms of which were filed as Exhibits to the Registration Statement.

The Notes will be issued pursuant to an Indenture attached hereto as Exhibit 4.1, to be dated as of the Closing Date between the Issuing Entity and Deutsche Bank Trust Company Americas, as Indenture Trustee.

The Notes evidence indebtedness of the Issuing Entity, the assets of which will consist primarily of motor vehicle retail instalment sale contracts (the “Receivables”) secured by new and used automobiles and light duty trucks financed thereby.

On the Closing Date, the Receivables will have the characteristics described in the Prospectus Supplement, dated as of November 21, 2013, to be filed with the Commission pursuant to Rule 424(b)(5) of the Act on or before November 25, 2013.

Legal opinions of Kirkland & Ellis LLP are attached as Exhibit 5.1 and Exhibit 8.1.

Item 9.01. Exhibits

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Dated: November 22, 2013

EXHIBIT INDEX