What's the 2002 Chevy Silverado 2500 oil type?

The 2002 Chevy Silverado works best with a fully synthetic motor oil. In fact, Chevrolet recommend using the 15w-40 viscosity motor oil from a reputable manufacturer for optimal performance and results. Fully synthetic oil is preferred, although semi-synthetic oils are acceptable. Fully synthetic oils offer a greater degree of protection, efficiency and performance and so offer more longevity and performance than a semi-synthetic alternative. Chevrolet recommends changing both the motor oil, as well as the oil filter every 3,000 to 5,000 miles if using a more conventional oil. If using a synthetic oil, be it fully synthetic or semi-synthetic, they suggest changing the oil and the filter every 7,500 to 10,000 miles.