Originally Posted By: FermeLaPorte
Check your head gasket
There would be potassium if coolant were getting into the oil. The sodium is from the high-sodium NAPA (really Valvoline, dexos1 Gen1 formula) previous oil changes.
About the drop in KV100 visc, a drop of 1.5 cSt here isn't that bad. Normally in 5k miles like this visc will drop, some from fuel dilution, and some due to VII breakdown, and then KV100 starts to rise as it passes around 7k miles due to oxidation beginning to happen (anti-oxidants breaking down, TBN getting low allows oxidation to happen more and more).