SAE Gear Oil Grade Table - Has it Changed Recently?

Joined
Sep 30, 2017
Messages
1,307
Location
Vancouver, BC Canada
Specialists out there, please humor me by answering my dumb question: Like the title says, has there been a recent change in the gear oil table?

I attach the first one (I don't know where I got it...) and if we want to focus say on 75W-80 - it says that (non-W) 80 wt has to be at least 7 cS viscosity at 100°C. If you look at the second table, it says the kinematic viscosity at 100°C has to be at least 8.02 cS. There are also changes in the 75W values... 4.1 cS versus 4.4 cS... ???? If I consider Pentosin MTF-2 it would be a 75W-80 according to the first table and not the second.

See the Pentosin bulletin, 3rd-up...

Anyone know what's going on?

Screenshot_2020-02-13-15-30-59-1.png


Screenshot_2020-04-09-21-35-56-1.png


Screenshot_2020-04-06-22-30-28.png
 
Last edited:
Originally Posted by Cdn17Sport6MT
Anyone know what's going on?


Could be a lot of years between those two sources. What's the spec today? ... that's what matters. Everything else is history.
 
So if this change is now in place - then when a mfr designed a transmission or transaxle originally... and spec'd an SAE lubricant weight/grade that was in play then... well, a person would have to apply a lubricant to that transmission now that DID meet the original spec'c range(s) of viscosity... Correct?
 
Last edited:
Seems to me that i) to the extent that bearing journal surfaces / bearings... and gear-to-gear contact faces would require min oil film thicknesses / properties that are related to the viscosities... and ii) the flow characteristics along drilled shafts / oiling funnel systems (for oil delivery to the running surfaces) - (and these two behaviours go in opposite "directions") are key. So a prudent owner that is "in-the-know" would choose lubricants now that are i) in the middle of the SAE viscosity ranges; and ii) that clearly do not fall outside of the original gear viscosity ranges that were in place at the time of the transmission design.

Effectively, the new specs are giving us heavier gear oil viscosities...?

Do I have this right?
 
Thread bump... any comments on this? MolaKule, Zeng, Others?

Here is a screenshot of a Lubrizol article, courtesy of bluefeb95. See the highlighted bump-up of non-W rated 80 weight...

Note, particularly, that the 75W value appears to be going DOWN, rather then up... i.e. the 80 wt is going up, the 75W goes down to 3.8 cS. It is contra to the trend happening in the first two graphics.

????

SAEJ306 Changes - Highlight - 80 Weight.jpg
 
Last edited:
Originally Posted by Cdn17Sport6MT
So if this change is now in place - then when a mfr designed a transmission or transaxle originally... and spec'd an SAE lubricant weight/grade that was in play then... well, a person would have to apply a lubricant to that transmission now that DID meet the original spec'c range(s) of viscosity... Correct?

First off, tribute to blufeb95 for the latest update on SAE J306 .

Yes as per original spec'ed , in accordance with the original selection by OEM's i.e earlier SAE classification, as intended .

Hence, IMHO SAE 90 OEM recommendation prior to 'splitting' in 2005 J306 classification should reference to gear oil KV@40*C of say, 220 - 320 cSt as originally intended .

Whilst OEM recommendation of SAE 80W90 multigrades prior to 2005 may be 'back-dated' (or forward-dated ?) to modern day GL4/5 of KV@40*C of 150 - 220 cSt .

Note: 2005 SAE J306 splits old SAE 90 grade to modern day SAE 90 and SAE 110 grades .
 
Originally Posted by Cdn17Sport6MT
...Thread bump... any comments on this? MolaKule, Zeng, Others?

????...


i am not clear as to your question.

Lubrizol has a good explanation;

Quote
...The revised SAE J306 standard, effective February 2019, better outlines the low viscosity grades for future manual transmission fluid and automotive gear oil requirements through the introduction of three new viscosity grades:

SAE 65
SAE 70
SAE 75
At the same time, the existing SAE 80 viscosity grade is being amended to tighten the broad kinematic viscosity window which currently exists.

Lowering the current minimum kinematic viscosity limit from 7.0 cSt to 3.8 cSt @100°C allows for new lubricants as low as SAE 65 to be utilized in conjunction with more modern hardware designs...

...Lubrizol views this revision with precise viscosity bands as a positive move, because it gives a framework to develop low viscosity fluids with the appropriate balance of efficiency and durability. The introduction of new lower viscosity grades provides the opportunity for more efficient automotive gear lubricants to work in harmony with advanced hardware designs, where the lubricant enables hardware design improvements as well as directly contributing to increased efficiency through its lower viscosity characteristics....



I happen to agree that since increased efficiency is being required, it give formulators more latitude in developing the lower viscosity driveline fluids.
 
Thx, but when original designs were conceived did the engineers not count on MOFT's (that correlate with viscosities)... and also shaft drillings lubricant flow properties (correlated to viscosities) - so that at-the-time-of-design SAE spec's - and their viscosities (as Zeng says) have to be used in thise gearboxes now? i.e. NOT current-spec SAE grade viscosities?
 
Last edited:
Originally Posted by Cdn17Sport6MT
Seems to me that i) to the extent that bearing journal surfaces / bearings... and gear-to-gear contact faces would require min oil film thicknesses / properties that are related to the viscosities...

Yes, by minimising frictional forces and frictional wear i.e aiming towards the right hand side of the Stribeck curve/lubrication regimes .



Quote
and ii) the flow characteristics along drilled shafts / oiling funnel systems (for oil delivery to the running surfaces) - (and these two behaviours go in opposite "directions") are key.

No .
In real life scenarios they are not in ' opposite directions' as automotive holes drilling is not in the realm of nano-scale miniature manufacturing if you get what I mean .


Quote
So a prudent owner that is "in-the-know" would choose lubricants now that are i) in the middle of the SAE viscosity ranges;

The logic makes sense in a way , but it is not always 'desirable' in automotive gear oil (ATF/MTF/axle oil) as one could select one viscosity grade beyond OEM recommended maximum/minimum grades to achieve a 'desired' outcome .

For example, I had replaced OEM recommended UTTO/UTF 5W30 GL4 grades (of KV@40*C 55-65 cSt) with a SAE140 GL5 (of KV@40*C 420 cSt) in non-hypoid gear trains vastly reducing (or eliminating ?) equipment breakdowns .

Optimum selection of automotive oil viscosity grades is always a compromise .
 
Last edited:
Back
Top