Just had a conversation with a tech guy at... a major oil brand. Long story short, the way he answered one of my questions strongly suggested that batch-to-batch variation was one possible reason they didn't list a sulfated ash number for one particular engine oil.
Anyone had a similar conversation, or know anything that corroborates this idea? I.e., that one possible reason for not listing a spec for an oil is that it varies too much from batch to batch?