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. But the old is thinner and GF-4, while the new is thicker (but with a better Pour Point) and GF-5. They also have a spec sheet for a new GTX 15W-40 UltraClean (there is also a current GTX 15W40 Modern Engine), but the new 15W-40 UltraClean hasn't appeared on their web page yet or in the shops. Any thoughts on the new GTX UltraClean oil ?