Quote:
Originally Posted by Vman455
The low temperature kinematic viscosity isn't necessarily identical. For example, Amsoil's Signature Series oils:
0W-20: 46.6 cSt@40C
0W-30: 58.2 cSt
0W-40: 85.7 cSt
Buuut...viscosity testing for the "W" designation happens at temperatures much lower than 40C, which aren't reported on any data sheets that I've seen.
|
I know this is an old-ish thread and all, but I've been searching and reading a bunch of old threads since joining recently. So, if it helps anyone following this thread or stumbling across it in the future...
The 40°C (104°F) viscosity isn't much of a low-temperature test, and is mostly a throwback to earlier days of oil standards. It does give you a glimpse of how thick the oil is along the way to being warmed up, but...
The 100°C viscosity rating is of more interest for operating temps. (And I have no doubt it was chosen in the beginning because boiling water is a really convenient way to heat up something to a stable 100°C.
)
The temperature used for the low-temp "W" rating depends on the rating they're going for, and there are two tests, pumpability (MRV) and cranking viscosity (CCS). So, for example, a 5W is tested at -35°C for pumping, and -30°C for cranking. At least one of these is usually provided on an oil's data sheet.
Hope this helps.