Originally Posted by Subdriver

For the daily driver, the 5w40 is probably a good balance between good cold flow and high temp performance and I'll consider that in my CTS-V once it is out of warranty.

I've also dropped you a PM with more info on the AMSOIL Preferred Customer Program

Originally Posted by Subdriver

My pleasure... and yep, actually still am - Nuclear Submarine Officer with 20 years active duty and counting... which is why I don't post for months at time frequently. Racing my Corvette (and the associate oil sales) are a hobby that I may take full time I retire, though not sure when that will be.

Originally Posted by Subdriver

My recommendation depends a little on that status of your warranty and whether you are willing to use an oil that doen't meet the owner's manual requirements. The LS2 requires an oil meeting GM Standard 47187M. This standard requires a synthetic oil of an xw30 multigrade. Unfortunately, the API's fairly recently introduced SM standard reduces the amount of ZDDP anti-wear additives these oil can use.

I personally believe the High Temp High Shear rating of an oil is a good indicator of how the oil will perform in the engine, particularly for those running the car hard. The High Temperature/High Shear Test measures a lubricant’s viscosity under severe high temperature and shear conditions that are similar to severe service applications in an engine. As such, in my 02 Z06 with an LS6, I run a 10w40, but I can afford to let my oil warm up before I go out on the track. That might not be practicable for a daily driver.

So... these oils are labeled by AMSOIL for use where GM Standard 4718M is called for, in order of decreasing cost/performance:
AMSOIL Signature Series Synthetic 0w30
AMSOIL SAE Synthetic 5w30
AMSOIL XL Synthetic 5w30

All three of these oils have an HTHS rating of 3.2. For comparison, the factory fill Mobil 1 5w30 has an HTHS of 3.09. FYI, I run the predecessor of the above 0w30 in my 06 CTS-V which has a stock LS2 under warranty.

If you are willing to forgo owner's manual requirements, I'd consider one of these:
AMSOIL SAE Synthetic High Performance 10w40 (HTHS 4.3 - this is the oil the thread starter chose for his ZR-1)
AMSOIL Synthetic 5w40 European Motor Oil (HTHS 3.7)

For the daily driver, the 5w40 is probably a good balance between good cold flow and high temp performance and I'll consider that in my CTS-V once it is out of warranty.

I've also dropped you a PM with more info on the AMSOIL Preferred Customer Program

Originally Posted by tmak26b

For tranny, I cant wait to get rid of the royal purple crap. I am debating if I should try Amsoil ATF, ATD or Redline D4