This discussion has been way too tame. Time to throw some gasoline on the fire.
Here is the "devils advocate" thought: Since one of the main functions of motor oil additives is to clean the inside of the engine, is it really a good thing when the oil stays perfectly clean. Of course, oil staying clean is an indication that everything is well with the innards, however, if one oil in the same engine stays cleaner than another, is that really a good thing?
I suppose that it would be possible for one oil to cause some sort of reaction that would cause it to be dirtier than another.
Don't get me wrong, I'm not an opponent of synthetic oil. But I've always taken the trail of changing the oil twice as often with an oil that costs half as much. When I take apart one of my engines, it is always very clean inside. It seems to work for me. And I'm sure that synthetic is working just as well or better for others.
'84 Euro 240D, 516K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in