Just purchased a 2013 GMC Sierra with the 5.3. What's everyone running these days? I have always been pretty old school with my stuff and did short oil changes for all my engines. I asked my friends father who has been a mechanic for over 40 years and he said he uses WolfsHead. I see they make a synthetic that meets Dexos approval. Anyone ever use this oil and have good results? Thanks in advance.