Late model cars have extremely tight engine tolerances to reduce engine emissions (crevices and pockets create unburned hydrocarbons). The bearing tolerances are tighter too. The theory regarding oil is that it is better to have it there than to have it thicker. Heavier oil may subdue hot, larger tolerances, but the thin stuff gets to the parts that need the lubrication and the tight tolerances result in a general loss of noise transfer. Synthetic oil also tends to stick to the parts better. On start up there is more of it where it is needed which helps to reduce noise and engine wear. I run synthetic in all my cars for just that reason. Between the limited starts/driving that the classics see and the short distance driving that my wife's car sees it protects better than "mother nature" oil.
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