Unless we're talking German 0w30, Mobil1 gets my vote. Otherwise, GC is great stuff, and use in my fathers VQ30.
I had some Syntec 5w30 that I put in my SL1 when I had it, it was the thinnest 5w I've ever used. the consumption was the highest with this oil out of any oil I've ever poured into that crankcase. And for the price, not interested in going that route ever again.