75w140 Synthetic vs 85w140 Conventional

[Canadastang]

I just had a Torsen T2R (the FR500 one with 4.0 bias ratio) installed about 1200km's ago and I'm going to do a break in oil change.

The installer advised me that Torsens shed a lot of material and to change the fluid often.

The car sees a lot of track time during the summer and then a mix of hwy/city driving.

3 quarts of synthetic 75w140 will cost me about $60-70 up here, yet I can get a 5 gallon pail of 85w140 conventional from Canadian Tire for $65. It's their 'in-house' brand, Certified, which I believe is made by SOPUS. This 5 gallon pail will probably net me about 8-10 diff fluid changes for the price of one synthetic. Here's the oil in question: http://www.canadiantire.ca/en/pdp/certified-85w140-extreme-pressure-gear-oil-20l-0280252p.html

My research tells me that synthetic oils in a torsen can reduce the bias ratio, and that many aftermarket diffs (True-Trac, etc.) were designed for conventional. Surely synthetic will give me (slightly) longer gear and bearing life, but I doubt if it will be cost-effective.

So, get the conventional and change it often or bite the bullet and go syn. and change it often as well?

 

[Jimzz]

I would do a Conv break in first then switch to the Syn.

Check walmart as they have 75w140 gear oil in the supertech brand. I used that when I had a Nissan titan that had diff issues.

 

[Canadastang]

Originally Posted By: Jimzz

Check walmart as they have 75w140 gear oil in the supertech brand. I used that when I had a Nissan titan that had diff issues.


Walmart in Canada used to have supertech; now it's been replaced with 'Tune it!' I have no idea if it's the same thing as Supertech, but that hokey name just makes me uneasy lol.

 

[zeng]

Originally Posted By: Canadastang
Surely synthetic will give me (slightly) longer gear and bearing life, but I doubt if it will be cost-effective.

Not true.
It's the opposite, in real life.
Quote:
So, get the conventional and change it often or bite the bullet and go syn. and change it often as well?

Yes, conventional ....... at oil change of say,40-60% of synthetic OCI, for components wear protection.
JMHO.

 

[beanoil]

I think it depends on your application. Ford spec is 75w140 in the Superduty rear, I ran Delo 85w140 in it. No issues, no performance difference as far ax I could tell. After 12k, the magnet had virtually no fuzz on it, and it drained clear. I think Delo has a superior conventional lube though with their Borate compound, you may find different results. I think you'll likely be fine with conventional and shorter OCI.

 

[Canadastang]

Thanks for the input everyone. I think I'll try the cheapo 85w140 and change it often.

 

[BrianF]

I run a group 4 synthetic 80w-140 in the real of my Ram 1500. Its Co-op brand, which I am unsure of the availability in your parts but its a Canadian made product easily found on the prairies. 9$ a liter and works great. I ran it for about 15 - 20 thousand KM which consisted of lots of heavy towing. I did a drain and fill with it to get a look at it after. Nothing on the magnet and it was barely discolored.

 

[dailydriver]

Originally Posted By: Canadastang
I just had a Torsen T2R (the FR500 one with 4.0 bias ratio) installed about 1200km's ago


COOL!!!

I WISH I could have had that diff in the axle of the car in my sig.

At least in the ST I have on order I can install either a Quaife, or Wavetrac diff, although they do not have the nice, HIGH bias ratio of that T2R.

Also, remember that although the Torsen type diff manufacturers may suggest mineral based/conventional gear oils, the 85W-140s will shear quicker (usually) than the synthetic based 75W-140s, despite generally starting out at a higher cSt @ 100*C, due to more VIIs added, especially when used for open tracking.

 

[zeng]

My limited reading is that a typical mineral 85W140 (usually of VI below 100) is VII-free, or of very negligible amount. Thus it 'should' be shear-stable but I'm yet to come across an UOA that demonstrate so.
However, a typical 75W140 probably contains VII's which I 'guess' is of far higher quantity than that of a typical 75W90 of quite similar base oil stocks.
That forms the basis of me usually recommending minerals 85W140 (and 80W90) over synthetics 75W140 and 75W90 for shear stability (over and above it's higher viscosity reading property) which is a highly desired property in gear trains for components protection and longevity.
Anyway, I could be wrong though.

 

[SavagePatch]

Originally Posted by zeng
My limited reading is that a typical mineral 85W140 (usually of VI below 100) is VII-free, or of very negligible amount. Thus it 'should' be shear-stable...


Any truth to this?

I'm debating between 75w140 syn VS 85w140 conv in my 2008 Mazda CX-9's troublesome Transfercase. Half quart capacity.

Thanks in advance!

 

[BrianF]

I just did a quick look at some oil specs for our locally made Co-op gear oil. Their conventional 85w-140 has a 100C cSt of 26.9, viscosity index of 106 and a -24C pour point.

Their 100% group 4 based 80w-140 has a 100C cSt of 27.9, 149 viscosity index and -42C pour point.

 

[domer10]

I just installed a true-trac rear diff, while they say use mineral (the company) they also say and many professionals on YouTube use redline GL5, from track to off-road....if 1000hp drag cars use it and it does not affect their bias then I'm sure it will be fine for our use. Don't think cheap when it comes to these fluids, I didn't spend 1500 on a new differential to use cheap bulk oil that I will have to double up on changes for peace of mind. Use the good stuff it works. I saw what cheap diff oil did with friction modifiers to rear lsd differential on jeeps, even changing it on time or early. And it has not effected performance at all, go out in snowstorms turn traction control off and could plow through anything, from stop the second I stepped on gas both wheels turning.

 

[Y_K]

I have 2 boxes of RL 80W-140 left. I use it only because I got it cheaply. Otherwise, it is Delo ES 85W-140.
I use M1 Delvac in transfer cases of Landcruisers.
Those 'heavies' are closer to what straight 90 used to be.

I would prefer marketing to finally use ISO numbers, but confusion sells in dumb markets better.

 

[neo3]

I recently changed to Valvoline semi-synthetic 85W140 in my 20 year old Camaro with a torsen diff. The owners manual specifically calls for synthetic, maybe so they can spec a longer maintenance interval. Before that was using Supertech 75W140 to try to fix what I thought was noise from the rear axle. Now that noise is gone, although I can't say for sure it was actually from the axle/diff. Anyway, with sem-synthetic you can make a compromise choice.

 

[zeng]

Originally Posted by SavagePatch
Originally Posted by zeng
My limited reading is that a typical mineral 85W140 (usually of VI below 100) is VII-free, or of very negligible amount. Thus it 'should' be shear-stable...


Any truth to this?

I'm debating between 75w140 syn VS 85w140 conv in my 2008 Mazda CX-9's troublesome Transfercase. Half quart capacity.

Thanks in advance!

Yes , in affirmation .
Shell S2 A 85W140 has a VI of 94 , others may have VI's of 96 or 98 .

They are surely 'free' of viscosity index improvers and I would consider them as being monogrades .
In relation to a differential, IMO a transfer case is of lighter duty hence should you consider a 85W140 , look at one with a KV@40*C of say, 350 - 390 cSt .

Edit:A typical 75W140 would deliver a low'ish KV@40*C of about 170 cSt , speaking about MOFT .

 

[zeng]

IME ,I'm quite sure the noise is helped by the thicker base oil and addpack with relatively higher operating viscosity/MOFT , never mind the weaker pressure-viscosity coefficient of a semi synthetic in relation to a mineral oil .

 

[userfriendly]

Because of the cold winters in Canada, the last 2 pails I bought were 80W140. One from Petro-Canada and the other Chevron.

Otherwise, zeng is right as rain.

 

[zeng]

Hence, you can kiss goodbye to differential whining noise comes 300,000 - 500,000 km odo , never mind heavy duty use or towing .