My father got a Silverado this summer..it recommends 0w-20. Had it a couple months and already more than 8,000 miles. It's the 5.3. He asked me the other day what he should put in it, so I'm relaying it to people who might know beyond just looking in the manual. I would normally tell him to just put in the specified grade and follow the OLM but it is DI, VVT, and has cylinder deactivation so I didn't know if it might require more from its oil. I want to say it is an 8qt sump. He's a general contractor so it's going to tow up to its rated capacity on a regular basis. He keeps his vehicles a long time. When it isn't suitable to DD anymore I guarantee it'll stay in the fleet as more of a "beater truck" but that will be a long time and a lot of miles from now. There is still a couple free changes yet but if there is any potential upside to bringing in a better oil for them to use it will be done that way. It's a remarkably smooth powerful and efficient engine. Makes sense to take care of it.