It may not be around much longer as I can't find any reference to SLX on Castrol's German or Australian web sites. They make reference to the 0W-40 and 10W-60 for full synthetics. The 0W-40 has the same HTHS @ 3.6 as GC and the viscosity at 100 = 12.9 whereas GC is 12.2, so it seems like the 0w30 may have been replaced.