Yeah, VI improvers are added to base stock oils by the manufacturer. I think the design of the PTU is what needs improvement. It is delivering torque to the front axles and the the rear driveshaft continuously of a 4500 lb car, using only a pint or whatever ridiculous capacity of oil. What remains to be seen I think is the effect on oil longevity with auxiliary water cooling equipped on interceptors and PP trim SHOs vs. non-cooled. Water cooling isn't even necessity. If you've got decent capacity, you can rely on a cooler, or even just cooling vanes on the housing to keep things cool. I've heard it's a headache to add the aux water cooling after-the-fact. Maybe it'd be easier to plumb in an inductive auxiliary oil cooler/radiator?
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