Oil weight reduction- ala Porsche Motorsport

[rsportvolvo]

Volvo, BMW and other manufacturers recommend a 15W-40/50 oil for extended high rpm use, i.e. racing. Unfortunately the extra protection comes with extra windage & pumping losses due to the higher viscosity oil. Porsche teams used to use Mobil 1 15W-50 for the GT3 Cup & GT3 RSR models, but they now use Mobil 1 0W-40. I first saw Posche Motorsport using Mobil 1 0W-40 oil with the Penske run RS Spyders. Now I see most Porsche GT3 teams with containers of Mobil 1 0W-40 in their paddocks. Does anyone have some tips for adjusting bearing clearances on older engines to allow the use of the lighter oil? Reducing windage & pumping losses is an area IT folks can exploit.