My problem with Castrol is how bloody vague their PDS's are, arg!
1. Castrol Edge 0w40 US PDS:
http://www.castrol.com/liveassets/bp_internet/castrol/castrol_usa/STAGING/local_assets/downloads/p,q/EDGE_Professional_European_PDS_July_2012.pdf
2. Mobil 1 0w40 US PDS:
http://www.mobil.com/USA-English/Lubes/PDS/GLXXENPVLMOMobil_1_0W-40.aspx
So, to compare:
1. Castrol Edge 0w40:
Approvals:
API SN/SM/SL/SJ/CF
ILSAC GF-5
ACEA A3/B4
BMW Longlife 01
Mercedes-Benz 229.3
Mercedes-Benz 229.5
Porsche A40
VW 502.00
VW 505.00
Specifications
Viscosity @ 100C, cSt 13.5
Viscosity @ 40C, cSt 79.3
Viscosity Index 169
Cranking Viscosity, cP (Max) 6,200 @ -35
Pumping Viscosity, cP (Max) ASTM D4684 60,000 @ -40
HT /HS Viscosity, cP min 3.5
Pour Point, F (C) max -76 (-60)
Flash Point, PMCC, C min >200
Density @ 15C, Relative 0.84
2. Mobil 1 0w40:
Approvals:
API SN/SM/SL/SJ
API CF
ACEA A3/B3, A3/B4
MB-Approval 229.3
MB-Approval 229.5
BMW LONGLIFE OIL 01
VW 502 00/505 00
PORSCHE A40
AVTOVAZ (LADA cars) AAE B6
Nissan GT-R
VW 503 01
SAAB
OPEL Long Life Service Fill GM-LL-A-025
OPEL Diesel Service Fill GM-LL-B-025
FIAT 9.55535 - M2
FIAT 9.55535 - N2
FIAT 9.55535 - Z2
Specifications
Viscosity @ 100C, cSt 13.5
Viscosity @ 40C, cSt 75
Viscosity Index 185
MRV at -40ºC, cP (ASTM D4684) 31,000
HTHS Viscosity, mPa•s @ 150ºC, (ASTM D4683) 3.8
Total Base Number (ASTM D2896) 11.8
Flash Point, ºC (ASTM D92) 230
Density @15.6 ºC, g/ml (ASTM D4052) 0.85
Mobil seems to be a lot more forthcoming with their product information rather than just using "min" or "max" figures.