Most Cobra guys are of the belief that thicker is always better. I'm convinced that if Castrol were to offer a 30W-60 most would switch to it.
For me, getting 60 PSI while using a 5W30
Synthetic is the best of all worlds. Plenty of pressure and
oil flow to move the heat. I would also have to think that the lighter
oil would put less stess on the distributor gears.
Bob