How often to change rear-end fluid '97 E300
 

I figured I'd ask the experts... How often is it recommended to replace the rear-end fluid in a '97 E300?

My car has just under 175,000 miles on her. Last time the fluid was changed at 124,000, when I first acquired the car.

There are no unsual noises, I was just curious. Is there any benefit to using Mobil 1 synthetic gear fluid, or should I stick to the OEM fluid, or is the OEM fluid synthetic?

Never HURTS (only costs $$) to do fluid changes! Any/all fluids have a "life" and should be changed IF you want LONG life from them!

Using synthetic fluids will extend fluid change intervals! Don't listen to that "LIFETIME" fluid fill CRAP!! Mobil 1 is a good choice for differential fluid change!

I abide by the same principals when I can as well. That's why I change the tranny fluid within 50k. I was just curious to if the synthetic stuff would allow for more slippage in the rear end and lead to premature failure if I've been running the standard fluid the entire time.

What weight should I use oil should I use?