Once you know the axle ratio, you can determine the correct gear oil weight. Generally, for a 2000 Chevy Blazer, you'll likely need either 75W-90 or 75W-140. 75W-90 is the most common and suitable for most conditions. 75W-140 is thicker and better for heavier loads, towing, or extreme temperatures.
Do not guess. Using the incorrect weight can severely damage your differential. Check your owner's manual or the differential tag for the definitive answer. If you can't find this information, a local auto parts store can assist you by checking your vehicle's identification number (VIN).
