2007 GMC Sierra 1500 Pickup Owner's Manual - Page 470

Adding Equipment to the Outside of Your Vehicle Things you might add to the outside of your vehicle can affect the airflow around it. This may cause wind noise and affect windshield washer performance. Check with your dealer before adding equipment to the outside of your vehicle. Fuel If your vehicle has a diesel engine, see "Diesel Fuel Requirements and Fuel System" in the DURAMAX® Diesel Supplement. For vehicles with gasoline engines, please read this. The 8th digit of your Vehicle Identification Number (VIN) shows the code letter or number that identifies your engine. You will find the VIN at the top left of the instrument panel. See Vehicle Identification Number (VIN) on page 598. If your vehicle has the 5.3L V8 engine (VIN Code Z), you may use either regular unleaded gasoline or ethanol fuel containing up to 85% ethanol (E85); also see Fuel E85 (85% Ethanol) on page 473. In all other gasoline engines, use only regular unleaded gasoline. Gasoline Octane For all vehicles, except those with the 6.0L V8 engine (VIN Code N), use regular unleaded gasoline with a posted octane rating of 87 or higher. If the octane rating is less than 87, you may notice an audible knocking noise when you drive, commonly referred to as spark knock. If this occurs, use a gasoline rated at 87 octane or higher as soon as possible. If you are using gasoline rated at 87 octane or higher and you hear heavy knocking, your engine needs service. Gasoline Use of the recommended fuel is an important part of the proper maintenance of your vehicle. To help keep your engine clean and maintain optimum vehicle performance, GM recommends the use of gasoline advertised as TOP TIER Detergent Gasoline. 470