Apparently there are two fluids in the front differential of the 997.2 C4 (and perhaps other models). One fluid is Porsche p/n 00004330300 which is a 75w80 lube. I have only found as Porsche branded at like $60 per liter. I guess it is not the same as the differential fluid you can find more commonly but which is 75w-90 and much less expensive.
So, 00004330300 is used for the AWD Controller Oil and is changed every 60K miles or 6 years.
The other fluid is the "differential" oil which is changed every 120K miles or 12 years.
Now all I need is a how-to for the AWD controller fluid change. Anyone, Anyone... Bueller. Dealer quoting around $450 for the change. I think it is just a couple of bolts.
sightline readers - great for working on your car if you use reading glasses.