I disagree.

If you use the correct fluid + the shaft and bearings are OK, the OE seals are good for several hundred thousand miles.

If the wrong fluid is used other seals will be damaged requiring system flush + rebuild, and the outer seal rubber composition is irrelevant.

If the shaft and bearings are damaged, the outer seal rubber composition is irrelevant.

.

We will agree to disagree.

Heat is the big killer of seals.
Interestingly on some power steering pumps the OE seals are viton. EG VM, & yes it was owned by MB at the time!

I have never had a MB PS pump seal failure though.

Had a few on tractors etc though.
All had correct fluid.
All had signs of heat degradation according to the equipment supplier.
Never had a viton one leak/fail apart from when the bearing next to it collapsed.

I will stick to pink seals over black ones & pay the premium. Same goes for O rings.

__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving

went to the dealer and bought one. if i'm looking at the correct side of the package, the part number for this part is: A 018 997 60 47

i took this seal to the local bearing supply store and they said it is not a normal seal size. the measurements listed on the seal are: 1B/CC 19.05x33.33x7.93/8.93

the part number on my power steering pump is 116 460 2780

i hope this information helps someone in some way.

__________________
1982 300sd from craigslist $800 greased on one tank with NO CONVERSION in the Hot Texas Sun. (currently dead & awaiting engine damage investigation and/or longblock swap)
new daily: '03 vw 5speed jetta tdi wagon. bagged&chipped