For a point of reference. I've been using Valvoline MST 5W-40 (DEXOS 2) in my ZL1 and oil sampling at every change. It has been basically flawless. The only flag I had was from some fuel dilution from taking a cold sample. The viscosity change for the 1LE is based on the potential for higher cornering forces. I've regularly hit 280 F oil temps during long track sessions.