2003 GMC Sonoma Owner's Manual - Page 307

Checking Brake Fluid You can check the brake fluid without taking off the cap. Just look at the brake fluid reservoir. The fluid level should be above MIN. If it isn't have your brake system checked to see if there is a leak. With the wrong kind of fluid your brake system, your brakes may not workwell, or they may not even work all. This could at cause a crash. Always use the proper brake fluid... Notice: Using the wrong fluid can badly damage brake system parts. For example, just a few drops of mineral-based oil, suchas engine oil, in your brake system can damage brake system parts so badly that they'llhave to be replaced. Don't let someone put in the wrong kind of fluid. If you spill brake fluid on your vehicle's painted surfaces, the paint finish can be damaged. Be careful not to spill brake fluid on your vehicle. If you do, wash it off immediately. See "Appearance Care" in the Index. After work is done on the brake hydraulic system, make sure the level is above the MIN but not over the MAX mark. What to Add When you do need brake fluid, use only DOT-3 brake fluid. Use new brake fluid from a sealed container only. See Part D: Recommended Fluids and Lubricants on page 6-32. Always clean the brake fluid reservoir cap and the area around the cap before removing it. This will help keep dirt from entering the reservoir. 5-44