7100 lb-rated new Silverado towing 4000 pounds

The 7100 lb. is gross vehicle weight rating, not tow rating. It has a gross combined weight rating of 12000 lbs. I have the 5.3 crew, 7200 gvwr and 15000 combined rating with 9600 tow rating with 1666 max payload rating and tow my 6500 lb. trailer with no problems. I average 19 non towing and 10 towing. Speed is the biggest factor in fuel consumption as it is the wind resistance that is the demon. I pull my rig at 55 to 60 mph at all times.