Differential Fluid
 

Hi guys,

In my 1990 300e, I run Mobil 1 engine oil and Mobil 1 trans fluid, both with good results. In the differential I currently run the recommended weight (forget what it is at the moment) hypoid gear oil. Anyone using synthetic in their differential? And, if so, to what result?

It's your choice, but the result is more profit for whoever you bought the synthetic oil, tranny fluid; gear oil from.

Absolute waste of money.

Conventional lubricants have carried many of us hundred of thousands of miles.

I just changed mine to Royal Purple synthetic 75W90. Guess I like paying more.
I run synthetics whenever I can.

Chris

Here's another way of looking at it... OEM is going to synthetic diff fluids, I believe for CAFE requirements. Apparently the premium cost for 1-2 qts synthetic diff fluid is offset by the small increase in gas mileage.

I am wondering too if synthetic will reduce the gear noise
in my W124 (87 260E). I was told by the mechanic that the
noise from the back when I drive is from the differential
which he says has been quite worn out. However he says you
can still drive it for years without any problems. However
the noise bother me sometimes. I wonder if I switch over
to something synthetic it would reduce it. If it does the
I think its worth teh money.

If your differential is indeed worn out, no lubricant in the world will make it quieter for very long. Synthetic lubricants are designed to have similar viscosity to their dino counterparts, but have a stronger molecular chain that stands up to high temperature better. Thus, they do not address gear noise. You will get a slightly quieter ride *IF* you haven't changed the fluid for a long, long time. But worn out is worn out - only a rebuild will make it better.