My Canadian friend you clearly don't yet understand the relationship between HTHS viscosity and kinematic viscosity. A higher HTHS vis' is not "better" it just means the oil is thicker regardless of what the KV100 spec' might be. That's why RL 5W-30 IS A 40WT oil in reality because a HTHS vis of 3.8cP is that of a 40wt oil. It's pressurized flow at all temp's is that of a 40wt oil. In comparison to M1 0W-40 it is a heavier oil particulatly at temp's below 100C despite M1's higher kinematic viscosity spec's. I pointed out the HTHS vs KV100 relationship to you in a recent thread on RL 5W-20 but I do it again. The following post explains why in more detail: http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2001169&page=1
Originally Posted By: jaj
[quote=Jeffs2006EvoIX][quote] I'm having the same debate myself with regard to a different engine. But its the same issue. My conclusion is that the "bulk viscosities" are what determine flow through most of the engine, and increasing that viscosity puts flow-dependent things at some risk. If your car has oil jets to cool the pistons, you might want to wonder how less flow at a higher viscosity might affect piston cooling, for instance. However, more HTHS is generally better than less. It's not a magic bullet, but it's a step in the right direction. So, if you use Redline, you get the same bulk viscosity as the factory recommended M1, with a substantially higher HTHS. Sounds like a win-win to me.