How does Castrol SAF-XO have such a low Brookfield viscosity?

[bulwnkl]

I have a very small (motorcycle) final drive that calls for SAF-XO. There isn't actually a spec, but the re-labeled product is still called SAF-XO. The data sheet I can find is here:

http://www.benquip.bz/uploads/products/files/SAF_XO_SAF_XJ_B1174_96.pdf

and you'll notice that the kinematic viscosities put it pretty squarely into the 75W90 range. However, look at the Brookfield viscosity: 42,900 cP. The few synthetic 75W90s I've looked at recently are FAR more viscous at -40. Does SAF-XO just have a slug of PPD in it or something?

Red Line's 75W90NS is about the same, though, as is their GL-4 75-90.

So that makes me wonder: What's the difference? Is that low Brookfield viscosity important above freezing (maybe down to 30F or so)? Why is there such a huge difference between Red Line's 75W90 and 75W90NS in terms of Brookfield viscosity? What additive (or lack of additive) makes this difference? Do I care?
Would the RL NS product be suitable for an application like this? Do I just ignore the Brookfield number and get some Mobil1 or something at the auto parts store, or is there some value in sticking with the SAF-XO?

BTW, Red Line recommends their Shockproof Heavy. That doesn't seem equivalent at all, but maybe they have other experience that leads them to that recommendation.

Appreciate any thoughts, and particularly informed comments.

 

[bulwnkl]

P.S.--
I'd be quite happy to use a Schaeffer product, or a Lubrication Engineers product, or others, but it MUST be available in a package no larger than 1 quart, and I won't buy more than 1 quart (because that's 3 changes in this final drive).

 

[FowVay]

That is a surprising difference in the MRV viscosities. I can only imagine that the numbers are so dramatically different due to the possibility of method of testing. ASTM D3829 tests pumping ability as does ASTM D2983. I don't know the exact differences in these two test methods but this may lead to the differences between a Brookfield reading and a MRV reading.

Also, I think the Castrol oil has been replaced with a product known as Transmax Axle Longlife 75W-90. This might be available from a BMW motorcycle center.

++ edit, I went back a looked at Redline 75W-90 GL-5 and 75W-90NS GL-5. The NS was listed for transmissions and had a Brookfield viscosity of 40,000cP. This may indicate that the Castrol product was actually designed for transmissions or light duty axles and not necessarily for hypoid axles.

 

[SuperSalad]

The few synthetic 75W90s I've looked at recently are FAR more viscous at -40. Does SAF-XO just have a slug of PPD in it or something?

I would guess no. If it were close to the limit, I'd be more inclined to believe there is a lot of PPD, but since it is so much lower than the 150,000 cP limit, I would say it is more likely just the nature of whatever base fluid they are using.

Is that low Brookfield viscosity important above freezing (maybe down to 30F or so)?

Not really, no. The moderate to high temperature viscosities are all pretty tightly close.

Would the RL NS product be suitable for an application like this? Do I just ignore the Brookfield number and get some Mobil1 or something at the auto parts store, or is there some value in sticking with the SAF-XO?

It looks like the NS would be suitable being a GL-5 gear oil. That is really your only concern along with viscosity. The requirement is the viscosity and GL-5 rating. The Mobil1 product would also be suitable at that rating.

BTW, Red Line recommends their Shockproof Heavy. That doesn't seem equivalent at all, but maybe they have other experience that leads them to that recommendation.

I was never a fan of the shockproof product, but that is just my personal opinion. The suspended solids made it nasty to deal with.

 

[bulwnkl]

Thank you both for your replies and input.

FowVay, they BMW m/c dealers are where one finds the SAF-XO product. (-:

I was never a fan of the shockproof product, but that is just my personal opinion. The suspended solids made it nasty to deal with.

Would you mind elaborating a bit? Was it problematic at all for the machine(s) you had it in, or do you mean cleaning it up in some context, or…?

I suppose I should (re-?)state a question in summary:
Is there a notable reason to _not_ use the SAF-XO product, other than potentially purchase price? This bike does not have high miles on it, but I intend to ride it quite a lot now that I have it, so I’d like good durability along with drive efficiency.

 

[SuperSalad]

It had pretty good performance, but the solids got sludgy and there was always a fairly thick layer on the bottom of whatever reservoir of oil it was. Took a ton of flushes to get it actually empty.

I'd say purchase price is the only reason why you might not want to use the SAF-XO product. I'm guessing it is VERY expensive coming from the dealer, where you can get a comparable product for much less.

 

[bulwnkl]

Your guess is correct. (-:

A cup of the stuff (what one needs for a fluid change) from a dealer is only slightly lower in price than a quart of the M1, for example. One can also buy a quart from the dealer, so then it's only 50 - 100% more than the aftermarket alternatives. So, it's not like it'll kill me to use the fluid in the manual. OTOH, it's much further away (or shipping) to get it, plus it costs more and is a bit more hassle than just going to any of several local shops where I can choose from M1, Red Line, Amsoil, Bel-Ray, Maxima, Motul, various others, and some house brands.

 

[MolaKule]

It had pretty good performance, but the solids got sludgy and there was always a fairly thick layer on the bottom of whatever reservoir of oil it was. Took a ton of flushes to get it actually empty.

I'd say purchase price is the only reason why you might not want to use the SAF-XO product. I'm guessing it is VERY expensive coming from the dealer, where you can get a comparable product for much less.

The reason being is that ShockProof oils contains a high level of calcium carbonates. I would not use in anything with a clutch or friction mechanism.

 

[MolaKule]

Your guess is correct. (-:

A cup of the stuff (what one needs for a fluid change) from a dealer is only slightly lower in price than a quart of the M1, for example...

What's this M1 you keep talking about??

 

[MolaKule]

I suppose I should (re-?)state a question in summary:
Is there a notable reason to _not_ use the SAF-XO product, other than potentially purchase price? This bike does not have high miles on it, but I intend to ride it quite a lot now that I have it, so I’d like good durability along with drive efficiency.

There is no reason Not to use the SAF-XO as I suspect the Brookfield viscosity is for best low temp operation.

 

[bulwnkl]

What's this M1 you keep talking about??

Mobil1's 75W90 gear oil; the stuff at the auto parts stores.

 

[bulwnkl]

There is no reason Not to use the SAF-XO as I suspect the Brookfield viscosity is for best low temp operation.

Okay, that works. I live in the Valley of the Sun, out by the White Tank Mtns, so it's never 'cold,' but perhaps I'll be in a cold place on the occasional morning.
(-:

 

[MolaKule]

Okay, that works. I live in the Valley of the Sun, out by the White Tank Mtns, so it's never 'cold,' but perhaps I'll be in a cold place on the occasional morning.
(-:

Yep, I know the area very well; Phoenix, Surprise, Waddell. I have hiked up WTM a few times. We go out to Festival Foothills (Buckeye) about once a year. Last summer we went to see some friends in Maricopa and Tucson; temps hovered about 108 for about a week.

 

[bulwnkl]

It had pretty good performance, but the solids got sludgy and there was always a fairly thick layer on the bottom of whatever reservoir of oil it was. Took a ton of flushes to get it actually empty.

I'd say purchase price is the only reason why you might not want to use the SAF-XO product. I'm guessing it is VERY expensive coming from the dealer, where you can get a comparable product for much less.

The reason being is that ShockProof oils contains a high level of calcium carbonates. I would not use in anything with a clutch or friction mechanism.

Considering this for a moment, would this cause a serious lube problem after a couple fluid changes? If the calcium compounds 'sit' in the gear case, then when you refill with new fluid, don't you have a new fluid _plus_ a bunch of leftover calcium from the previous fill? After a couple or few drain-and-fill cycles, wouldn't that be a problem? Or, does it not build up in that way over time (and drain-and-refill cycles)?

 

[MolaKule]

Considering this for a moment, would this cause a serious lube problem after a couple fluid changes? If the calcium compounds 'sit' in the gear case, then when you refill with new fluid, don't you have a new fluid _plus_ a bunch of leftover calcium from the previous fill? After a couple or few drain-and-fill cycles, wouldn't that be a problem? Or, does it not build up in that way over time (and drain-and-refill cycles)?

It might take a few drain-and-fills to remove the calcium sludge.

 

[bulwnkl]

That is a surprising difference in the MRV viscosities. I can only imagine that the numbers are so dramatically different due to the possibility of method of testing. ASTM D3829 tests pumping ability as does ASTM D2983. I don't know the exact differences in these two test methods but this may lead to the differences between a Brookfield reading and a MRV reading.

Also, I think the Castrol oil has been replaced with a product known as Transmax Axle Longlife 75W-90. This might be available from a BMW motorcycle center.

++ edit, I went back a looked at Redline 75W-90 GL-5 and 75W-90NS GL-5. The NS was listed for transmissions and had a Brookfield viscosity of 40,000cP. This may indicate that the Castrol product was actually designed for transmissions or light duty axles and not necessarily for hypoid axles.

So, I grabbed a PDS for the Transmax Axle Longlife product (not listed for nor apparently available from Castol in, the USA), and its Brookfield isn't as low as SAF-XO, but it's still quite low at ~50,000 cP.

Maybe one take-away here is that gear oils formulated for limited-slip diffs have rather high Brookfield viscosities, whereas ones formulated explicitly for NON-limited-slip diffs seem to have relatively much lower Brookfield viscosities.

Again, is that an additive consequence, or does one blend bases that differently merely due to limited-slip vs non-?

 

[bulwnkl]

It might take a few drain-and-fills to remove the calcium sludge.

Drains-and-fills with a non-Shockproof product, is that what you mean? If one simply used Shockproof over and over, might that be a problem?

 

[MolaKule]

Drains-and-fills with a non-Shockproof product, is that what you mean?...

Yes.

 

[930.engineering]

Also, I think the Castrol oil has been replaced with a product known as Transmax Axle Longlife 75W-90.

True. Castrol SAF-XO has been replaced by Castrol Transmax Axle Long Life 75W-90:

https://msdspds.castrol.com/bpglis/FusionPDS.nsf/Files/B0B1E2992B03889C8025849C00411F6A/$File/BPXE-BHBVWN.pdf

This might be available from a BMW motorcycle center.

Any BMW dealer. BMW still sells it under its old name SAF-XO.

Castrol SAF-XO/Castrol Transmax Axle Long Life 75W-90 is PAO based, which
explains its very low pourpoint and Brookfield viscosity. Which of course is a
good thing. Generally Castrol's fully synthetic transmission oils are excellent.

.​

 

[bulwnkl]

I was at a BMW m/c dealer today to pick up a small part, and saw the C-SAF-XO on the shelf. I picked it up and saw that the label says “Made in USA” on it. Since neither of the Castrol fluids under discussion is marketed in the USA, this caused me to think the fluid therein is neither SAF-XO nor Transmax Axle LongLife, but rather something that BMW NA here substitutes.

Is this a reasonable supposition? Should I assume that BMW NA (the importer) has an equally complete spec to what BMW Germany uses, or is it more likely they use whatever Castrol markets in NA (or some other contract blender)?