I went through this fire drill back when my '88 190E 2.6 was less than a year old. I recall that MB recommended an axle fluid change early on. There was a list of approved oils in my owners documents. I searched high and lpw for a recommended Pennzoil product, but couldn't find it anywhere.

I finally called Pennzoil and they said that particular product was NOT SOLD in North American. I chewed the service manager a new one over that.

Bottom line is that a Mercedes hypoid axle either with an open differential or limited slip is the same technology as most front engine, rear drive cars regardless of country of origin, and the recommended axle oil is a generic API spec: SAE 80W-90 GL5, and it's readily available. Brand makes no difference. Just make sure you buy a product that has the API "donut" with the above spec contained therein.

If the diff is a limited slip (clutch type ,what GM calls Positraction) you'll need a 4-oz. bottle of friction modifier. Mercedes sells it, but so does NAPA (NCB 4285V) and just about any other parts chain under their own part numbers

I went through a similar deal over recommended oil for the manual transmission, but that's another story.

Duke