Since synthetics cost the consumer way more than regular oil there is no economical advantage aside from any gained protection factors. And for folks who thought they could run synthetic 15-20,000 miles before changing they forgot to amortize the cost of adding more oil- say a quart every 2-3,000 miles. So how do you end up with the same oil in 15,000 miles after you add 5-7 quarts during that time at $4-5 a pop? And you still gotta change filters too.

There is no cost benefit per mile in synthetic. If you believe in their chemical superiority in engine protection that's another thing. But there is no plus for the average daily commute vehicle. I know people with performance vehicles that use synthetic and change it at no more than 3-5,000 because they believe it is better stuff and cost be damned.