Mixing & pour point = do I get an average?

[SpitfireS]

As the title says, if I mix some leftover SAE 90 with a -24C pour point with some SAE 85W-140 with a pour point of -12C in a 1:4 ratio do I get (4x12 + 24 = 72, 72/5 = )-14.4C?
I guess it works with viscosities, does it also work like that with pour points?
The leftover SAE 90 has an additive I wanted to mix into the 85W-140 and I wanted to lower the pour point a little.

Besides all this, a 85W-140 with a pour point of only -12C is not realy a 85W oil.. I think.
According to the MSDS it's a mineral oil.

Anyway...
Thanks for reading

 

[JHZR2]

In reality, if you want to be thermodynamically consistent, you must calculate the gibbs free energies of mixing, and determine various properties based upon activity and thus fugacities from there, to decide where two phases begin to occur.

This is likely impossible from an experimental standpoint.

Given the overall similarities of the chemistries of the base fluids, a numeric average is likely acceptable for determination.

The best thing to do is attempt an experiment. Most of the tests done for this sort of stuff are relatively simplistic. Your freezer can surely do -12C, likely -24C as well.

JMH

 

[SpitfireS]

Originally Posted By: JHZR2
Your freezer can surely do -12C, likely -24C as well.
JMH

It was in the freezer as I was checking this thread

After a good 3 hours @ -21C the mixture turned kinda solid, as a thick sirup, not like a grease.
Then I left it outside for the night @ -2C or so and in the morning it still flowed (as expected).
Right now its in the differential.

 

[Eddie]

I read that mixing gear lubs is not recomended.

 

[INDYMAC]

Why don't you just buy some LE 1605 and be happy?

 

[SpitfireS]

Mixing is bad?
For the same reason(s) mixing engine oils is bad?
IMO my "mixing" is not more then adding some leftover oil to get an additve into the original oil.
I agree that the levels of that additve may be too low to actually work, but I don't think it would hurt the original oil.

@ INDYMAC

I'm trying to find the LE-1606 locally as the manufacturer of my final drive (Richmond Gear) recommends a 75W-140.

The LE-607 that was in the diff produced very little shavings (more a powder) on the magnetic drain plug so it worked ok.
I did notice a little less gear noice with the 85W-140 (with a dash of LE-607)

As soon as I am able to buy the LE-1606 its going in, no doubt.
If I can't... then I have to think about getting the Castrol SAF-XJ 75W-140 (locally) or the LE-1605 (online - IF they ship overseas)

Finding good products (or good on paper

)online is easy.
Getting them in your hands is .... not easy.

 

[unDummy]

I've never had any problems with mixing.
Visc isn't simple math. But, you did thin out the 140wt with the 90wt a little.

I also have no faith in pour point specs. Read Amsoils gear oil and ATF paper. We'd be lucky if all fluids meet the specs they claim to meet.

Use a full synthetic 140wt. This will give you the thick oil protection with reasonable pour point.

What application is this for? How cold does it get in winter?

 

[SpitfireS]

Originally Posted By: unDummy
Use a full synthetic 140wt.

The LE-1606 is a single grade SAE 140.
According to the LE website its a semi-synthetic.
If I can get my hands on that my quest is over.
Originally Posted By: unDummy
What application is this for?

The Honda S2000 differential.
Originally Posted By: unDummy
How cold does it get in winter?
Winters overhere usually get as low as -5 overnight with the occasional -10C.
Lower temps do occur (-15C) but maybe only every other year for 1 night.

Last couple of days I've been looking at Shell Spirax A LS 85W-140 and the Shell Omala RL 320.
Omala is an industrial POA gear oil by Shell.
It doesn't have an API spec but I doubt it won't meet it as industrial specs are just as tough.
Shell tested it according to ASTM D2266 (4-ball weld load) @ > 210kg.
IMO that's good enough for a diff.
And it has a pour point of -45C !