1978 manual recommends 10 or 20W oil for stick shift?

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Looking through the owner's manual for my '78 Mercedes 300D, with a 4-speed manual trans. the recommended oil is a 10 or 20W engine oil. Later manuals (early 80's) call for ATF.

Having already drained the fluid of the Dex/Merc ATF I put in when I got the car, I found some Supertech SAE30 rated CF/SG and filled with that. Shifts are a bit "thicker" but not prohibitively so and no bad behaviors showed up.

What's the scoop on older boxes that recommend ATF, motor oil, etc.? What type (synthetic, conventional, older API rating or not) is going to satisfy the intended friction characteristics, etc.? Does a product like Redline MTL or Amsoil Synchromesh have any benefits/drawbacks in these applications?
 
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Looking through the owner's manual for my '78 Mercedes 300D, with a 4-speed manual trans. the recommended oil is a 10 or 20W engine oil. Later manuals (early 80's) call for ATF.

Having already drained the fluid of the Dex/Merc ATF I put in when I got the car, I found some Supertech SAE30 rated CF/SG and filled with that. Shifts are a bit "thicker" but not prohibitively so and no bad behaviors showed up.

What's the scoop on older boxes that recommend ATF, motor oil, etc.? What type (synthetic, conventional, older API rating or not) is going to satisfy the intended friction characteristics, etc.? Does a product like Redline MTL or Amsoil Synchromesh have any benefits/drawbacks in these applications?
I imagine a learned person or two here could find what the dynamic and kinetic viscosity equiv. in gear oil is - to 10W or 20W motor oil. I suspect something like 70W manual transmission / transaxle lubricant is equiv. I would ensure it is GL-4.

BTW, nearest I can tell - in North America in 1978 - the 300D was only avail. with a 4 spd A/T. So either you are not in North America or the car has been converted-over. Neat!

I now see you are in Ky... So mebe the car is a euro import?
 
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This is interesting never heard of one taking oil for a transmission and I’ve worked and owned many old things.
Really? I had a 1976 Ramcharger that took 10w30 in its transfer case and Trans. Honda used 10w30 in them in the manual transmissions in the 80's and 90's. My scout ,IHC pickup and my currant f250 take sae 50 motor oil in the trans.

 
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Really? I had a 1976 Ramcharger that took 10w30 in its transfer case and Trans. Honda used 10w30 in them in the manual transmissions in the 80's and 90's. My scout ,IHC pickup and my currant f250 take sae 50 motor oil in the trans.

Wow had no idea on any of that. Learn new stuff everyday.
 
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pretty much all european cars in the 60s used engine oil for the gearbox. 90wt gear oil was for diffs. sae80 came in and gradually took over, as did ATFs.

a modern multiweight gear oil would probably work good
 
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Alex_V

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I imagine a learned person or two here could find what the dynamic and kinetic viscosity equiv. in gear oil is - to 10W or 20W motor oil. I suspect something like 70W manual transmission / transaxle lubricant is equiv. I would ensure it is GL-4.

BTW, nearest I can tell - in North America in 1978 - the 300D was only avail. with a 4 spd A/T. So either you are not in North America or the car has been converted-over. Neat!

I now see you are in Ky... So mebe the car is a euro import?
It's a euro-spec car, supposedly brought over from the Netherlands in '84. Still has its original bumpers, headlights, and license plate! Cloth interior, manual climate control w/o air conditioning, no cruise or tinted glass, and I believe it didn't even have a radio originally.
 

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pretty much all european cars in the 60s used engine oil for the gearbox. 90wt gear oil was for diffs. sae80 came in and gradually took over, as did ATFs.

a modern multiweight gear oil would probably work good
A friend had an Austin Mini in the late '70s. He said the engine and manual transaxle shared the same 5-quart (Imperial, so 6-quart US) sump.

Can't remember, but presume he used 10W-30 conventional like the rest of us did.
 
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Many sources recommend conventional 5W-30 for the transmission in my '85 Laser. Guys on the forums highly recommend Redline MTL, which I installed a couple of weeks ago. It made a huge difference. I've read discussions highlighting that motor oil isn't ideal for proper synchro operation. I think that proved true in my car.
 

Alex_V

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Many sources recommend conventional 5W-30 for the transmission in my '85 Laser. Guys on the forums highly recommend Redline MTL, which I installed a couple of weeks ago. It made a huge difference. I've read discussions highlighting that motor oil isn't ideal for proper synchro operation. I think that proved true in my car.
This was one of my suspicions, especially considering the changes in motor oils since the 80's that have made them slicker, etc.
 
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Dug up an old 240d manual since the 300d manual didn't mention manual transmission fluid

Talk about pathetic techwriters that don't understand SAE J300 prefix/suffix charts.

Lets translate this:
SAE 10W /20 W-20

I'd guess they meant 10w20, 20w20, or 20, or 10W..... maybe they were thinking ISO 32, 46 or 68, that somewhat match the labeling nightmare.

20 repeats and without the W and would be a ~6.9-9.3cst fluid.

I might consider a quality non-multivehicle ATF, like Allison TES389 or 295/668 for conventional/synth choices. But, these old motor oils usually had the classic level of zddp so maybe I'd avoid the ATF choices.

If would lean toward any synchromesh fluid.... Amsoil MTF, Redline MTL thinned with MTL-LV, BG Syncroshift2, and of course the Valvoline/Pennzoil Synchromesh fluids. I don't remember these ol' transmissions being picky or being so weak that fluid was critical.

Valvoline/Pennzoil/GM synchromesh have my vote here, or a trip down to the Honda dealership for their MTF.
 
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Synchromesh would have a similar viscosity to an SAE 20 oil.

My '85 F250 with Borg Warner T19 4 speed took SAE 50. Tons of people used 80w90 gear oil in those units and I've never heard of any issues.

I don't believe the older motor oil spec gearboxes are very picky. You could probably run most any oil of the appropriate viscosity without any ill effects. I'd be curious to know if the additives in a synchromesh fluid might contribute to better shifting or less wear.
 
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Dug up an old 240d manual since the 300d manual didn't mention manual transmission fluid

Talk about pathetic techwriters that don't understand SAE J300 prefix/suffix charts.

Lets translate this:
SAE 10W /20 W-20

I'd guess they meant 10w20, 20w20, or 20, or 10W..... maybe they were thinking ISO 32, 46 or 68, that somewhat match the labeling nightmare.

20 repeats and without the W and would be a ~6.9-9.3cst fluid.

I might consider a quality non-multivehicle ATF, like Allison TES389 or 295/668 for conventional/synth choices. But, these old motor oils usually had the classic level of zddp so maybe I'd avoid the ATF choices.

If would lean toward any synchromesh fluid.... Amsoil MTF, Redline MTL thinned with MTL-LV, BG Syncroshift2, and of course the Valvoline/Pennzoil Synchromesh fluids. I don't remember these ol' transmissions being picky or being so weak that fluid was critical.

Valvoline/Pennzoil/GM synchromesh have my vote here, or a trip down to the Honda dealership for their MTF.
It's a little thinner than a thin SAE20, but RL 70W/75W is GL-4 and about 6.5CSt at 100C
 

MolaKule

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I too would recommend a modern, dedicated MTF. Motor oils were specified before the dedicated MTF's came onto the market.

Any of the fluids listed below should work:

Sntrans V FE (8.0cSt)
Redline DCTF Dual Clutch Transmission Fluid (8.1 cSt)
BG Synchroshift II (8.2 cSt)
Valvoline MTF Part Number 811095 8.8 cSt
RAVENOL PSA (8.9 cSt)

The next higher viscosity MTL group in the 9.0 to 9.5 cSt range is (SAE 75W80):

Mopar Type MS-9417 MTL 9.0 cSt
Pennzoil Synchromesh 9.0 cSt
RAVENOL SSG 9.5 cSt

The next group of MTL’s are in the 9.6 to 10.X cSt range (SAE 75W80):

Redline MTL 75W80
Amsoil MTF (9.7 cSt)
GM Synchromesh’s
Volvo MTF 645
Fuchs TITAN SINTOFLUID SAE 75W-80 synthetic MTF (Carries a GL-5 rating as well)
Lodexol (Morris Lubricants) MTF
Motylgear 75W-80
 
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During 1997 MB stopped filling up their gearboxes with ATF and started using a 75w or 75w80 synthetic (Bevo sheet 235.10). From my experience, too thick a fluid can really make MB manual gearboxes hard to shift in cold weathers, i had bad experiences with some thick 75w80. A 20w translates to a 75w in the world of gear oils. A good 75w always worked well for me, just make sure you pick a GL4 gear oil and avoid GL5. ATF works well too and seems to be the universal fluid for Mercedes manual transmissions, older and newer. My 240D 5 speed always had ATF, so does my E250 D and zero gearbox related problem. A friend switched to ATF in his 6 speed W204 and he told me it shifts better now when the car is cold. I know high mileage cars (W123, W124, W202, W210...) and never heard of a gearbox related issue except for it being hard to shift (especially 1st and 2nd) when the car is cold. Issues are always related to the shifter bushings or the clutch.
 
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