Had my 2016 Silverado 5.3L in for service, and decided to let them change my oil as it was free, and I had heard that AC Delco 0w-20 was now a full synthetic where before it was a semi-syn. I was looking at the invoice and was trying to verify the fill was correct, but I can't find specs for the part number listed. The part number used for the oil is 88864004. Not going to panic if it's the older stuff, but just want to know going forward. Appreciate any help.