Originally Posted By: dailydriver
Originally Posted By: A_Harman
Many people on the GM websites advocate German Castrol, which is where the 12cSt number comes in. Some say the thicker oil helps with piston slap, others don't. One of the oil mixes that is on my list to try is M1 0w40/0w30. These two can be blended to get the target 12cSt KV100, but will have a higher VI than the vaunted GC.
We (LSx owners) all know the much vaunted 12 cSt number (WHY I mix the two Red Line grades), BUT, has
anyone ever come up with a matching 'magic'
HTHS value for our engine group (stock internals, of course)??!!
I tend to think that since GM specs 5w30 for the LSx engines, they're OK with the API min HTHS of 2.9cP. But since I like to have some margin, I would add 10% to that to allow for shear as an oil ages, and end up with 3.2 for a new oil. Regular M1 5w30 I think is 3.1, so maybe it's close enough. But M1 HM 5w30 is 3.3, so would be good to go. And then there is Redline 5w30 at 3.8, probably way more film thickness than the engine needs.