w123 240D benz. What oil for diff and 4speed?

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Apr 3, 2005
Hello all.

Im working on my "new" 240D with 328K miles on it. It has a 4speed manual transmission.

The manual says to use 10w20 oil. Ive never seen this weight before and I wonder if the new SM oil will be bad news in this unit.

And for the diff it says to use 85w90..That should be easy to find but would there be any advantage to going with another weight in this high millage rear? It doesnt seem to me making any funky sounds.

Run Mobil 1 75w-90 in the diff. It has impressive cleaning capability and has done well in LOTS of w123 owners' cars. Id also use amsoil 75w-90 with confidence.

As for the MT fluid, there likely is a relatively low viscosity, MT-specific fluid, sold by amsoil, redline, or otherwise, which will do well. I cannot make a recommendation, as Ive not been lucky enough to have an MT-equipped w123.

I wonder what the dealer specs as the right fluid. MB dealers are very good at having the data and parts for very old models. They may be able to give you very good info, and so it is likely worthwhile stopping by the parts desk, or calling a dealer.

Phil at Mercedesshop may also be able to help.
Any synchromesh mtl/mtf would meet the 20wt spec for the manual.

Any 90wt GL5 would work in the rearend.
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