Is a SL oil superior to an SJ when it comes to cold weather operation. Now they are run the ccs at -30c instaed of -25c. Example Pennzoil 5w-30 SJ was 3300 ccs at -25c, now at -30 it is 6600 ccs. Is 3300 at -25c better than 6600 at -30c???
The rule of thumb (from Lubrizol) is that a petroleum oil thickens by a factor of 2.0 for every 5C drop in temp. For a PAO/Ester based synthetic, it is a factor of 1.7 for each 5C drop in temp. This will allow you to find the approx CCS visoosity at different temps.
Most of the newer formulations I've seen are actually slightly thicker if you use this conversion.
Patman posted an excellent link on this subject in another thread:
On page 8 it explains that while CCS viscosities are measured 5 deg C cooler, the maximum viscosity limit doubled. From their explanation this is a relaxation of the previous standard, but I don't understand why. Seems to me to be a tie.