My family owns a 2001 Chevrolet Silverado 2500 HD with the 6.0 liter Vortec engine. It has 64,000 miles on it with 5W-30 oil. The oil was changed at 60,000 miles and in 4 months it burned 1 and a 1/2 quarts of oil. We also towed a car for about 1,000 miles during that 4 months. Is all this normal or is there a problem? Thanks
