It's recently arrived in Australia too
https://bobistheoilguy.com/forums/ubbthreads.php/topics/4269898/
But I don't know much about it.
Originally Posted By: SR5
So I have just noticed a new Castrol GTX 10W-30 in the Australian market. It's called "UltraClean" and right now it's sold in parallel with the older GTX 10W-30 "Modern Engine".
NEW: GTX 10W30 UltraClean
API SN and ILSAC GF-5, claims to offer 50% better sludge protection than industry standard.
KV40 = 73 cSt, KV100 = 10.8 cSt
PP = -45C, FP = 200C, SAPS = 0.95
CCS @ -25C = 6414 cP
OLD: GTX 10W30 Modern Engine
API SN and ILSAC GF-4, claims to offer 25% better sludge protection than industry standard.
KV40 = 61 cSt, KV100 = 10.1 cSt
PP = -36C, NOACK = 13%, HTHS = 2.9 cP
CCS @ -25C = 4000 cP
In usual Castrol fashion, their PDS sheets give a fairly random selection of oil characteristics, some of which may be nominal rather than measured. It's common to see: HTHS 2.9 min, PP -36C max, FP 200C min, so I wouldn't put too much weight in those values when given, except to mean the min/max requirement has been met. But the old is thinner and GF-4, while the new is thicker (but with a better Pour Point) and GF-5.
Also I've just noticed that the Oz Castrol web page is titled "Castrol GTX Part Synthetic", so I assume this new oil is a Group II and Group III blend. While the older oil is probably Group II only.
Also a flyer I have says the new UltraClean is 50% cleaner "compared with API SN Seq. VG Sludge test limit". In reality I would assume that many other name brand SN & GF-5 mineral oils would beat this limit by a decent amount. However I also assume the older GTX (SN & GF-4) beat it by 25%, so this is a decent improvement for Australia.