It really doesnt matter what oil you use anymore. It's been 10w30 on the cap from 95-03, then 5w30 because of a different oil pressure spring. 5w30 meets the requirements of 10w30 from way back.

But in reality everyone just runs 5w30 because of the climate they live in, the reason for it not leaking/seeping as much is as good as saying your guess is as good as mine.