My engine holds 6qts of oil.Does anyone know how much synthetic oil is in Castrol SynBlend? I bought a 5qt container and 1 qt of the CSB (5W20) at Walmart last night.Would it benefit the engine any better if I were to replace the 1 qt with 1 qt of SynTec Edge,or just run the 6qts of SynBlend and leave it at that?