GMC Yukon 2021 Owner's Manual page 399

398 Technical Data
5.3L V8 Engine (L84)
6.2L V8 Engine (L87)
Spark plug gaps are preset by the manufacturer. Re-gapping the spark plug is not recommended and can damage the spark plug.
Engine Drive Belt Routing
If the vehicle has a diesel engine, see the
Duramax diesel supplement.
5.3L and 6.2L Engines
Engine Specifications
Engine VIN Code
D 0.95 1.10 mm (0.037 0.043 in)
L 0.95 1.10 mm (0.037 0.043 in)
Spark Plug Gap