Is GL4 MB 235.1 80W manual trans oil correct for S211?

[MJJ]

Morning all,

I recently changed the manual gearbox oil on my S211 E220CDi, as the car has 177k and I don't know if it has ever been changed. No symptoms or issues pre change, just unsure of the mileage on the old oil. Since the oil change, it is harder to select 1st, 2nd or 3rd when the gearbox is stone cold. It feels like the clutch is not fully disengaging, but goes after a mile of driving with some heat in the oil.

Choosing the right gearbox oil has been confusing. I found it impossible to fathom a straight answer from WIS, the Haynes manual states 'Mercedes Benz specification MB345.0 part no. A 001 989 24 03' , E.g. Pentosin CHF 11 S' . I had assumed the Haynes spec. was a misprint as CHF is hydraulic fluid (eg. PAS system), not transmission. Looking up that part no. also shows hydraulic oil.

After some Googling, I decided to use a Castrol manual transmission 80W oil meeting Mercedes standard 235.1, this oil in fact. Oil change was straightforward, and it took 1.7l (Haynes states 1.6l capacity) of new oil.

Does anyone know if the oil I chose is incorrect, and I should be using something else? My gut feel is this issue is co-incidental, and I do have an issue with the clutch hydraulics perhaps, but puzzled as to why a mile worth of heat in the gearbox oil makes the problem go away.

Thanks for any advice,

Martin.

 

[ivan1983]

Is it possible that you have over filled the box, on the manual box in the slk they updated the service instructions by reducing the fluid required by 100ml to improve shifting

 

[MJJ]

Is it possible that you have over filled the box, on the manual box in the slk they updated the service instructions by reducing the fluid required by 100ml to improve shifting

Thanks, that is interesting - I am surprised that 100ml makes a difference. It is entirely possible that mine is 100ml over, I set the level by filling until the new oil overflowed out of the fill plug but as per my first post, it did take 100ml more than the Haynes manual thinks the capacity should be.

If others think that the oil I used is correct, then I will get under it again and see if I can remove 100ml.

Martin.

 

[190]

An 80W is too thick for a modern MB manual box which I suggest your symptoms demonstrate as the change improves when the oil warms up.

I agree the specs are confusing. You need to look up your gearbox type in sheet 231.1 and that will give you the right oil spec. I concluded that the correct spec for my manual transmission NMT 370 is 235.3 which is a 75W oil and a fair bit thinner than your 80W

MB 231.1 - Specified gear oils (cars, cross-country vehicles) - overview - Mercedes-Benz Specifications for Operating Fluids

Finding a 235.3 oil is another story because there aren't many available but Castrol do an FE 75W which is the correct viscosity and not too hard to find.

 

[MJJ]

@190 , thank you for that - hugely helpful. I am surprised that 75W vs. 80W would make a noticeable difference, but given my symptoms, it must do.

Martin.

 

[190]

Hi Martin,

The difference in viscosity is much bigger than the grade numbers would imply.

Your Castrol 80W has a viscosity of 85.6 cSt @40 deg C while the Castrol FE 75 is only 32 cSt at the same temperature. When cold the difference may be even greater.

 

[MJJ]

Hi Martin,

The difference in viscosity is much bigger than the grade numbers would imply.

Your Castrol 80W has a viscosity of 85.6 cSt @40 deg C while the Castrol FE 75 is only 32 cSt at the same temperature. When cold the difference may be even greater.

I just wanted to post back and say thank you @190 , I changed the gearbox oil for Febi 75W and the difference is vast. All back to normal, and I have learned a lot here regarding the practical differences between seemingly-minor viscosity spec differences.

Martin.

 

[Gazwould]

As above , massive cold centiStoke difference .


Other suitable products albeit from two specialist oil manufacturers .

The Millers is thinner again as @ 40°C is
28.9 cSt .