Shell has improved the quality of their GTL base oils to Group III+++ level, with Noack going a lot lower than in the past PurePlus GTL-based Pennzoil formulations. Castrol still has the worst base-oil quality among major brands as usual—they use the cheapest Group III−−− base oil they can find. Castrol has worse base-oil quality than Fram has in this case.
To get the comparative base-oil quality, I look at Noack × CCS in the same SAE viscosity grade, the lower being the better.
To get the comparative base-oil quality, I look at Noack × CCS in the same SAE viscosity grade, the lower being the better.
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