ORIGINAL: dbacque

The reduced surface drag due to dimples is minimal. The real reduction comes in the reduction of pressure drag due to separation of the boundary layer.

When the airflow over a surface is laminar, the boundary layer separates earlier creating more drag. When the airflow over a surface is turbulent, the boundary layer separates later so there's less drag. The bottom line is turbulent airflow over a golf ball's surface creates less drag.

The dimples act as turbulators, they create turbulence near the surface and thus reduce the pressure drag due to separation.

But 12% better mileage? I'd question their results. If it worked that well on cars we'd all be driving dimpled cars.

Dave