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0w30 is bad juju for GM motors IMO...
I haven't seen any UOAs that indicate German Castrol 0w30 is "bad juju" for LSX motors. For one thing, they seem to do okay on M1 5w30 which is thinner than GC. For another, the bad UOAs discussed in this thread are for one LS1 that's been "rebuilt by GM" and another that is a performance "built" motor. The rebuilt nature of these 2 motors introduces many unknowns as to how these engines were rebuilt and what parts were used. There is the possiblity that the "rebuilt by GM" motor was actually rebuilt by a dealership tech who didn't do it to the same high standards as the factory. And the performance "built" motor could have been rebuilt with looser tollerances in search of performance, which could affect UOAs v a nice tight stock factory LSX engine.
In summary - i think the bad UOAs on Chris B.'s car are more likely due to the fact that the LS1 was "rebuilt by GM" than to any problem with GC in an LS1.
Now if you'll excuse me, I'm off to pick up an oil filter and switch my 130K mile M1-5w30-changed-every-3000 LS1 over to GC