Power steering fluid

[col320ce]

ATF vs Power steering fluid.  Kent form Mercedes source suggests that ATF causes excessive wear.  Any thoughts?  I have MB Q-1-46-0002 fluid on the shelf!
Thanks ...

[Pawel66]

quite a lot of discussions on this topic, e.g.: https://www.sl113.org/forums/index.php?topic=27816.msg202314#msg202314

[Peter]

The 280SL owner’s manual suggest to use far as I remember “Castrol TQ” for the Power Steering and the Automatic Transmission.

Is there also a “special ATF” needed for the automatic Transmission? I’m now using “Mobile ATF 320”.

[WRe]

Hi,
see MB 236.2, Type A Suffix A transmission oil.
...WRe

[MikeSimon]

Where exactly does "Kent" say the "excessive wear" occurs? I worked for two of the major manufacturers of hydraulic power steering pumps and would like to hear more about that theory.

[col320ce]

This is the link to kent:
https://youtu.be/TLR_kdnsJ_0

[wayne R]

I have used Prestone  power steering fluid, for more than 30 years ,in all makes and models,
in US, NZ, and Australia, my opinion its the best , go to google,look at
the results and proof.-----Made in Illinois USA.

[Peter]

Hi,
see MB 236.2, Type A Suffix A transmission oil.
...WRe

Interesting information, Thanks.
Do you have same MB xxx,x information about the rear axle oil?

[Benz Dr.]

I've been using ordinary ATF in everything for years. I use Synthetic in my own car but everything is in that application. Relative to my having no problems at all, what's the concern here? 

[Pawel66]

Interesting information, Thanks.
Do you have same MB xxx,x information about the rear axle oil?

Mercedes SAE 85W90  MB 235.0, capacity 2,5l
1l canister  PN A000989030411  AOHW

[WRe]

Hi,
the power steering fluid Kent recommends is Febi 08972 which corresponds to Dexron II and MB 236.3: https://partsfinder.bilsteingroup.com/de/article/febi/08972.
Nevertheless MB maintenance manual for cars from 1/68 says MB 236.2 (same for automatic transmission).
...WRe

* https://bevo.mercedes-benz.com/#cb_betriebsstoff_vorschriften

[specracer]

Well I used synthetic ATF (I had it on the shelf)....

[MikeSimon]

The first automaker that used hydraulic power steering was GM Oldsmobile. When it became really popular in the 50s, GM specified a hydraulic fluid and ATF Dexron was chosen, because they did not want to add another fluid to the service dealer inventory which had very little usage. The hydraulic power steering system requires little lubrication. There are no fast revving parts under high load. The vanes in the pump, running with their tips against the phosphate coated ring contour hardly need any oil. ATF is sufficient for that purpose. The reason many manufacturers "specified" a unique power steering fluid was a marketing gimmick. Unique brand product - additional charges to the end user.
The only drawback ATF showed was poor cold climate performance and some automakers, e.g.: BMW introduced a fluid called "Pentosin" for their "arctic" applications. Mean stuff! Needs to be handled carefully. Many techs showed severe skin irritation after handling it.

[Benz Dr.]

The first automaker that used hydraulic power steering was GM Oldsmobile. When it became really popular in the 50s, GM specified a hydraulic fluid and ATF Dexron was chosen, because they did not want to add another fluid to the service dealer inventory which had very little usage. The hydraulic power steering system requires little lubrication. There are no fast revving parts under high load. The vanes in the pump, running with their tips against the phosphate coated ring contour hardly need any oil. ATF is sufficient for that purpose. The reason many manufacturers "specified" a unique power steering fluid was a marketing gimmick. Unique brand product - additional charges to the end user.
The only drawback ATF showed was poor cold climate performance and some automakers, e.g.: BMW introduced a fluid called "Pentosin" for their "arctic" applications. Mean stuff! Needs to be handled carefully. Many techs showed severe skin irritation after handling it.

Wouldn't synthetic kind of take care of really cold weather problems?

[MikeSimon]

Dan: I am not sure if synthetics in general could remedy the problem. All p/s fluids are being qualified to work from -40° to +140° Celsius (-40° to + 285°F) Synthetic fluids usually do no offer an advantage at low temps. Their strength is protection against lubrication capability breakdown over time and at higher temperatures.

[Benz Dr.]

Dan: I am not sure if synthetics in general could remedy the problem. All p/s fluids are being qualified to work from -40° to +140° Celsius (-40° to + 285°F) Synthetic fluids usually do no offer an advantage at low temps. Their strength is protection against lubrication capability breakdown over time and at higher temperatures.

That's exactly what they do. They flow better at low temperatures. I've been using synthetics for 38 years - I know what they can do.

[MikeSimon]

Dan: I tip my hat to 38 years of experience. We poor sods who spend a good amount of our young lives in engineering school always keep learning and it never stops.
The capability of ANY fluid to perform at extreme ends of the temperature spectrum is expressed by a rating of its kinematic viscosity, usually called "centistoke" cS. Thus, there are synthetic oils that are better at low temps and there are some that are worse. Generalizing the capability is like saying a V8 is faster than a V6.

[WRe]

Hi,
here some little facts/history about ATF transmission oil, source "Automotive Lubricants Reference Book", Caines/Haycock.

The first transmission comparable to present automatic type was Oldsmobil Safety Transmission of 1937, superseeded in 1939 by the first fully automatic transmission, the Oldsmobil Hydromatic. Following problems after recommendation for the use of engine oil as the working fluid, a new type of fluid with better low-temperature characteristics was designed by GM research togehter with Mobil. Buick pioneered the replacement of a simple fluid coupling with a torque converter type called Dynaflow in 1948 very similar to those of today. Similar transmission were developed by GM, Ford and Chrysler.

With the introduction of the torque converter more heat was generated in the transmissions and an improved type of fluid was required. In 1949 GM issued their "Type A" specification for a fluid, which in turn was succeeded by "Type A Suffix A" in 1957, which is the MB recommendation for our transmissions.
These were initially the standard specifications for transmission fluids, but Ford in 1960 and Chrysler in 1964 issued their own specifications while GM again introduced an improved fluid known as DEXRON in 1967.
Ford's and GM's fluids have been upgraded several times mainly in terms of improved oxidation and stabilty requirements, with the Ford fluid initially having significantly different frictional characteristics from the GM fluid. But more recent changes brought their fluids more in line with those of GM. Following complaints of "clunk" on low-speed changes, Ford modified their policy in 1978 and introduced a friction-modified fluid which was later called MERCON. There are now only minor differences between frictional requirements of GM's DEXRON II and III specifications.

At the present time ATF are normally petroleum based although synthetic varieties exist. A complex blend of additives is required to meet the various specifications as oxidation, corrosion and rust inhibitors, metal deactivators, anti-wear and seal agents, viscosity and friction modifiers and dispersants.  It can be seen that an ATF is more complex than that of a motor oil.

...WRe