2004 GMC Envoy Owner's Manual - Page 312

You should keep a record with all parts receipts and list the mileage and the date of any service work you perform. See Maintenance Record on page 6-16. 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. {CAUTION: You can be injured and your vehicle could be damaged if you try to do service work on a vehicle without knowing enough about it. • Be sure you have sufficient knowledge, experience, the proper replacement parts and tools before you attempt any vehicle maintenance task. • Be sure to use the proper nuts, bolts and other fasteners. "English" and "metric" fasteners can be easily confused. If you use the wrong fasteners, parts can later break or fall off. You could be hurt. Fuel Use of the recommended fuel is an important part of the proper maintenance of your vehicle. Gasoline Octane Use regular unleaded gasoline with a posted octane of 87 or higher. If the octane is less than 87, you may get a heavy knocking noise when you drive. If this occurs, use a gasoline rated at 87 octane or higher as soon as possible. Otherwise, you might damage your engine. A little pinging noise when you accelerate or drive uphill is considered normal. This does not indicate a problem exists or that a higher-octane fuel is necessary. If you are using 87 octane or higher-octane fuel and hear heavy knocking, your engine needs service. 5-4