2008 GMC Envoy Owner's Manual - Page 343

What to Use To determine what kind of lubricant to use, see Recommended Fluids and Lubricants on page 6-12. Bulb Replacement For the proper type of replacement bulbs, see Replacement Bulbs on page 5-54. For any bulb changing procedure not listed in this section, contact your dealer/retailer. Headlamp Aiming Headlamp aim has been preset at the factory and should need no further adjustment. However, if your vehicle is damaged in a crash, the headlamp aim may be affected. Aim adjustment to the low-beam headlamps may be necessary if oncoming drivers flash their high-beam headlamps at you (for vertical aim). If the headlamps need to be re-aimed, it is recommended that you take the vehicle to your dealer/retailer for service. Halogen Bulbs {CAUTION: Halogen bulbs have pressurized gas inside and can burst if you drop or scratch the bulb. You or others could be injured. Be sure to read and follow the instructions on the bulb package. 5-49