Quote Originally Posted by Eevo View Post
I disagree with you on this part Rick.

90% of engine damage is done in the first minute.
0W oil provides the best cranking viscosity.


so if your engine is designed for a viscosity of 10.
at 24 degrees
0W has a viscosity of 40
10W has a viscosity 100

neither of the them provides enough protection, but 0W is a lot closer then 10W!
I wrote out e really long reply on the phone yesterday at lunch, saved it as a draft to edit last night and promptly lost it !

I know that 90% number has been touted for years, and Castrol had numbers to support it but I don't totally buy it as

1) what temps were they testing at ?
at -25*C, yes, I can see it, but at a +5*C start, Hmm...

2) If that was strictly the case, we'd all be running 0W-20 engine oils, saving fuel, making more power and reducing wear, (because 90% of wear is at start up) but real world figures don't support it

At above 0* the kinematic viscosity between a 5W and 15W with the same hot SAE grade isn't that great, and depending on the oil sometimes the 15W may have a lower actual viscosity until the temps get below 0, it all depends on base oils and viscosity index improvers.

I just can't be arsed putting some numbers through a VI calculator atm, might do it tonight.