[Zeke]

Revisiting this thread.

So, between cash and Lube, nothing has been said that is definitive. Lube does discuss the flow vs. heat issue, but then backs away from from the issue saying, "...the reported viscosity weight was actually not correct. The fortunate side of this is that be going up or down one grade it has little effect on engine performance..."

He also states the weight on the bottle is not always correct.

OK, so what we need is some control here so that the weight is verified and 40w is tested against 50w brand for brand and group for group to see if 40w does offer more cooling (or not) in a oil cooled engine.

It is my submission here that 40w pure synthetic is a better choice up to severe conditions like full on racing for the air (oil) cooled 911 motor. It certainly offers the protection the factory specifies for a water cooled boxer engine that runs high temps for emmisions control.