Here is the info for my 1995 C280:

1.2 US quarts; 1.1 liters

Hypoid Gear Oil SAE 90, 85w 90

Good luck! BTW, I did use synthetic gear oil when I had mine changed. I actually had to buy 2 bottles because each bottle was 1 quart. THerefor, I got 1 quart of synthetic, and one quart dino. I used all of the synthetic, and filled the remainder with the dino.

I might give the dealer a call to make sure that 1996 MY was the same.

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2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)