When you read a oil data sheet what significance does the ammount of suffated ash have? Some oil makers such as Pennzoil dont even list it. Castrol listes as 0.90 in the GTX, 0.85 in syntec, and 1.2 in GTX Startup, Valvoline lists it at .80 and Motorcraft 5w20 is at like.86. Does this have something to do with the cleanness of the oil or what does this represent? Thanks.