Originally Posted By: 2KBMW
Tucson Five-O. How about neither. A better low cost oil
in my opinion is Valvoline Synpower. It is not all grp III
like the others. It's -42 C pour point and 4000 cP @ -30 C
ccs spec. prove this. It does carry the GM 4718 oil spec
that you want. It's viscosity of 10.5 cSt vs 9.7 cSt of
Castrol will not make much of a difference in fuel economy.
I would rather have a higher viscosity oil where you are
anyway.
Pennzoil Platinum is tested at -35C, rather than -30C (big difference) and has a viscosity of 5,150 cP vs the Synpower which is tested at -30C for that number of 4000.
Pennzoil Platinum and Valvoline Synpower 5W-30's are both tested for MRV viscosity at -35C, where the Platinum does 14,800 cP, and the Synpower does 18,600.
PP 5W-30 has slightly better numbers for cold weather. The 100C viscosity of PP is 10.3, and Synpower is 10.5
PP wins IMO.