Mega 75w-90 testing thread!

SubieRubyRoo said:
Not many applications seem to call for them, and the folks that do have them never seem to test them.

However, I do have to ask, do you have an application that calls for a 140 grade gear oil? The 75w90 HPL is robust enough that Richard Petty’s car haulers use it with no failures, that seems pretty stout to me?
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For me I only use 140 weight gear oil in my brush shredder gear box, the steering box and front axle of my tractor just so they leak slower. The subject of "how long it lasts" is kind of irrelevant.
I use 140 to top off my dodge Dakotas diff. I figure adding a bit of 140 to it's usual 90 weight will make up for any shearing loss. It's a dodge so it leaks and it gets a squirt of gear oil in it's rear end every engine oci. Again, how long the 140 weight gear oil lasts kinda doesn't matter.
 
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SubieRubyRoo said:
You may want to check how Ravenol DXG fared in my 3.5 EcoBoost. Hint: it didn’t stay in grade after only 6k miles and the TBN was depleted as well.

Ravenol’s gear oil may be a little better, but I wouldn’t go more than 30k without in-service sampling.
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I have some EPX 80w-90 and MTF-1 75w-85 coming out of my 3IS soon and will send to Blackstone. I am confident there will be no issue. Too many variables unfortunately to look at a single test from a totally different vehicle/driver/application. My only gripe with oil analysis, especially where the temp doesn't reach something like the inside of an engine. Nevertheless, I'll give it a look.
 
SubieRubyRoo said:
@ford250 @SNWMBL @Impatient and maybe more (sorry, it’s been awhile!) contributed samples for this test.

We’ve imported the other 75w90 tests from my other thread here, and also add these 75w90s:
Shell Spirax
Subaru HP
Ultra Plus (cool clear bottle!)
AC Delco
Valvoline Synpower
Ravenol VSG
HPL non-CC Diff Life

Somehow, I misplaced the Motul Motylgear so that didn’t get submitted. Apologies. Lab also included foaming results, but I have not read the ASTM method yet to determine the pass/fail criteria. Looks like vsl= visual, and tr= trace. Other than that, here’s the two data sets with a few reporting differences, new stuff on top. I’ll see if they recorded all the Brookfield and pour point data so the overall data is the same… Enjoy!


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SubieRubyRoo said:
@ford250 @SNWMBL @Impatient and maybe more (sorry, it’s been awhile!) contributed samples for this test.

We’ve imported the other 75w90 tests from my other thread here, and also add these 75w90s:
Shell Spirax
Subaru HP
Ultra Plus (cool clear bottle!)
AC Delco
Valvoline Synpower
Ravenol VSG
HPL non-CC Diff Life

Somehow, I misplaced the Motul Motylgear so that didn’t get submitted. Apologies. Lab also included foaming results, but I have not read the ASTM method yet to determine the pass/fail criteria. Looks like vsl= visual, and tr= trace. Other than that, here’s the two data sets with a few reporting differences, new stuff on top. I’ll see if they recorded all the Brookfield and pour point data so the overall data is the same… Enjoy!


View attachment 198679View attachment 198680
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Good morning, I don't know how to make out the foam test and the PDSC min. I guess what I'm asking, witch one of these are under performing?
 
Foaming test you’d be best served to review the appropriate test guidance. Maybe another member who’s more in depth with it can comment. My limited experience shows foam does not lubricate, so the quicker an oil can remove bubbles, the better it is.

As far as PDSC goes, it is merely a time result that shows how long it takes an oil at a specific temperature and pressure to oxidize the oil. The higher the PDSC number, the longer it will take the oil to start oxidatively thickening and possibly start creating deposits.

You unfortunately can’t take the PDSC value and use it as a relative performance tool- say if one oil achieved 7 minutes and one got 42 minutes, you can’t say the 2nd oil will last 6X the mileage.
 
Fa24wrx said:
I put the subaru 75w90 in at just under 25k miles. Original still looked great. I'll do amsoil at 40k probably
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Generally speaking, the Subaru diffs are not that hard on gear oil. Between the AWD & the variable center diffs there’s not a huge load on them so they’re usually just fine at 50k intervals. Nothing bad about sooner changes if you want though.

STi’s and manual cars are a little bit harder on gear oil due to clutch drops having a higher shock. But even then if you’re using a good synthetic and haven’t pulled & significantly modified the engine, diffs will not be the first failure on any Subaru drivetrain.👍🏻
 
SubieRubyRoo said:
Generally speaking, the Subaru diffs are not that hard on gear oil. Between the AWD & the variable center diffs there’s not a huge load on them so they’re usually just fine at 50k intervals. Nothing bad about sooner changes if you want though.

STi’s and manual cars are a little bit harder on gear oil due to clutch drops having a higher shock. But even then if you’re using a good synthetic and haven’t pulled & significantly modified the engine, diffs will not be the first failure on any Subaru drivetrain.👍🏻
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So run this oem fluid for a little? It still looked relatively "bright" at almost 25k. Maybe another 25k run on this round and change again at 50k to Synthetic?
 
Fa24wrx said:
So run this oem fluid for a little? It still looked relatively "bright" at almost 25k. Maybe another 25k run on this round and change again at 50k to Synthetic?
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I’m well-documented as being a Motul Gear 300 fan in Subaru diffs, and I still say it’s a good option if you don’t mind overpaying for a very good but not great gear oil. I used to go 50k with no worries and no UOAs on it because it came out nice and clear. Now I’ve switched to HPL and will go 100k with fewer worries than with the Motul. YMMV, but the data’s pretty clear. Motul < HPL Diff Life.
 
SubieRubyRoo said:
I’m well-documented as being a Motul Gear 300 fan in Subaru diffs, and I still say it’s a good option if you don’t mind overpaying for a very good but not great gear oil. I used to go 50k with no worries and no UOAs on it because it came out nice and clear. Now I’ve switched to HPL and will go 100k with fewer worries than with the Motul. YMMV, but the data’s pretty clear. Motul < HPL Diff Life.
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I guess you'd avoid that valvoline that's on sale right now?
 
SubieRubyRoo said:
I’m well-documented as being a Motul Gear 300 fan in Subaru diffs, and I still say it’s a good option if you don’t mind overpaying for a very good but not great gear oil. I used to go 50k with no worries and no UOAs on it because it came out nice and clear. Now I’ve switched to HPL and will go 100k with fewer worries than with the Motul. YMMV, but the data’s pretty clear. Motul < HPL Diff Life.
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Not sure if I mentioned but my wrx is the manual version as well
 
SubieRubyRoo said:
My biggest issue with the Gear 300 in a stick in subzero temps is it can be nearly impossible to get into 1st gear on cold starts. Those first few shifts are as hard as permafrost tundra.
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I live in Georgia, so no worries there. How's the motul compare vs amsoil? I contacted HPL about getting the right gear oil for my wrx but never heard back
 
Fa24wrx said:
I live in Georgia, so no worries there. How's the motul compare vs amsoil? I contacted HPL about getting the right gear oil for my wrx but never heard back
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I don't specifically know your 6 speed MT and oddly Amsoil doesn't directly address the MT. I assume it's still a shared front diff MT?

I had the junker 5 speed MT in my 2014 WRX. Shared front diff. Hard on fluid, really was. Change at least every 25K miles.


https://www.amsoil.com/p/amsoil-sev...thetic-gear-lube-svg/?code=SVGPK-EA?zo=515729
 
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