The oil companies have changed their oils they sell to the public alot over the last 50 years. I don't remember exactly when you could buy synthetic at Wal Mart, but it had to be in the last 20 years. Don't kid yourself. The oil cos have 1 thing in mind when making oil to sell to us...How much profit?!? Of course they have to meet minimum standards that are made by a consortium of auto makers, oil cos, and the Feds. And they have to be competitive in quality and price. So, your question of why don't they add zMAX (or Duralube, PTFE) to their oils? Good question. But I say it has more to do with money than any other consideration that may benefit the consumer.
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