The 4.3 V6 in your truck is the same engine that spec'd SN/GF-5 conventional in 2010, prior to dexos. Buy the Conoco and forget about it. dexos is another way for GM to make money. Seriously, I'm not hating on the brand, but it's a money maker more than it's an oil requirement. I wouldn't hesitate to run plain conventional in a brand new EcoTec 3 in a Silverado.