Motul Gear 300 & HPL Differential Life 75W90 VOA comparison!

I wasn’t familiar with PDSC, had to look it up. That was the most different result between the 2 lubes…other than viscosity. I presume bigger number is better???
Missed this before. Short answer: yes, longer time to oxidation is better. It took the HPL roughly 7 times longer to begin oxidizing with 500psig oxygen and a temp between 130-210*C. But the catch to this ASTM test is that it does not correlate directly to service life in any way.

ASTM D6186 said:
“This test method covers the determination of oxidation induction time of lubricating oils subjected to oxygen at 3.5 MPa (500 psig) and temperatures between 130 and 210°C.”

Informative paper on PDSC:
 
You guess correctly. But, like I’ve previously offered, I’m not asking for donations for the testing. Just the quart of Redline; I’ll donate the quart of SG 75w90.
This what you need ?
 

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I think both the Subie’s you mention are the newer design that don’t need the “extra help” the older 5-sp needed, so I agree, my mix would not appeal to you. i’ll go out on a limb here and say the HD 5-sp relied more on “splash” lubrication, whereas the newer WRX had a pump of some sort??? Or narrow galleys maybe??? I don’t know which the Forrester 6-sp is closer in design to: the hi-perf 6-sp, or the hi-perf HD 5-sp…or maybe neither. I was aware of the “mix” controversies when I put my mix in, and can assure you I was hesitant too, but have been impressed…but this applies only to the hi-perf 5-speed…such as found in 2004-2009 Outback XT and Legacy GT (other than Spec B…which had the hi-perf 6-sp). I don’t know which “Impreza-based“ models got that 6-speed, maybe only the STI, nor which Imprezas, if any, got the HD 5-sp, but I’m way too far OT and in the weeds.
All non-STi transmissions are similar in case design and synchro/final drive size, the late 6 speeds in the Forester/Legacy(Outback)/Crosstrek/WRX have the same center plane split case and lack of oil pump that the early 5 speeds have. Late 6 speeds have various different mount styles and cable shifters instead of direct rod shifters when compared to the 5 speeds but nothing like STi. Even only the first years of USDM STi have oil pumps, either 07 or 08 was the break, I don’t remember.

The two architectures shift very differently with the same fluids. I have had no reason to switch from, or complain about, Motul Gear 300 75W-90 in a 90k used STi, now at 184k. (That said, I don’t believe Gear 300 can be purchased right now, so that is an issue for my overdue oil change).

I have been battling to get my 5 speed to shift “tolerably” by my feel standards. Straight Gear 300 felt too light and crunchy when hot. I drained a quart and refilled with Redline Lightweight Shockproof and ran that for 15k. I just tried to dump that and swap it for a more Shockproof- heavy mixture and my aftermarket front LSD didn’t like the lack of friction modifiers in the Shockproof. It’s temporarily happy enough with a full drain and refill of dealership Subaru synthetic HPGO 75w-90.

I don’t know if any of this is useful to folks here but it’s all been experientially gathered by myself with my own cars in the last 5 years, not from the internet.
 
Subie,

When are you chiming in with shift feel feedback with the new magic juice in your car?

Are there analysis numbers that would indicate what the high pressure/friction modifier additives are in the two samples you tested?

Highly interested for my Subie fleet - 480hp STi, 5 speed dual range fully LSD/locker Outback
 
All non-STi transmissions are similar in case design and synchro/final drive size, the late 6 speeds in the Forester/Legacy(Outback)/Crosstrek/WRX have the same center plane split case and lack of oil pump that the early 5 speeds have. Late 6 speeds have various different mount styles and cable shifters instead of direct rod shifters when compared to the 5 speeds but nothing like STi. Even only the first years of USDM STi have oil pumps, either 07 or 08 was the break, I don’t remember.

The two architectures shift very differently with the same fluids. I have had no reason to switch from, or complain about, Motul Gear 300 75W-90 in a 90k used STi, now at 184k. (That said, I don’t believe Gear 300 can be purchased right now, so that is an issue for my overdue oil change).

I have been battling to get my 5 speed to shift “tolerably” by my feel standards. Straight Gear 300 felt too light and crunchy when hot. I drained a quart and refilled with Redline Lightweight Shockproof and ran that for 15k. I just tried to dump that and swap it for a more Shockproof- heavy mixture and my aftermarket front LSD didn’t like the lack of friction modifiers in the Shockproof. It’s temporarily happy enough with a full drain and refill of dealership Subaru synthetic HPGO 75w-90.

I don’t know if any of this is useful to folks here but it’s all been experientially gathered by myself with my own cars in the last 5 years, not from the internet.
Well, I appreciated it. At least I’m not the only nutball on here who tried Motul & LW Shockproof. I was hoping HPL Dave might understand what I was getting at, but that’s a tall order…to respond regarding a mix of 2 competitors’ products, especially with a “weird” fluid like the Shockproof.

does anyone know why Motul Gear 300 is constrained?
 
This what you need ?
Well, some (or many) people might want to see that tested, but there is also a RedLine 75w90 without friction modifiers…confusingly labeled 75w90NS.
 

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Subie,

When are you chiming in with shift feel feedback with the new magic juice in your car?

Are there analysis numbers that would indicate what the high pressure/friction modifier additives are in the two samples you tested?

Highly interested for my Subie fleet - 480hp STi, 5 speed dual range fully LSD/locker Outback
Oh… there may have been some details you missed between some of the other threads that led to this. Quick rundown: I have the Motul because when I used to have stick Subies, this went in the trans and the diffs. I found Gear 300 notchy in the trans when super cold and sometimes hard to get in 1st when just started in Midwest winters but never really had issues when hot. Since I’ve only had 4EATs in my most recent OB & Impreza, the Gear 300 I’ve bought over the years has lasted longer, so I had a quart I would sacrifice for a few members’ info prior to buying.

On the flip, I just bought some HPL Green CC atf, Differential Life, and No VII Euro 5w30 for my ‘19 F150 which is obviously a much more highly stressed application than 173 crank HP minus slushbox losses then divided four ways 🤣

So, unfortunately I won’t be able to offer any shifting impressions, but I will be sending both Amsoil and Redline 75w90s for testing as well. @ford250 is donating a quart of the Redline, so props to him! 👍🏻
 
Haven’t been able to find it anywhere in stock for months, is what I assume - that’s what I’ve experienced
Ok… supply chain shortages. I’ve seen the same thing.

The nice thing about HPL is that they keep nearly all the raw materials on-site for all their normal products, and can literally blend on-demand and have it in the mail same or next day! 👍🏻
 
Oh… there may have been some details you missed between some of the other threads that led to this. Quick rundown: I have the Motul because when I used to have stick Subies, this went in the trans and the diffs. I found Gear 300 notchy in the trans when super cold and sometimes hard to get in 1st when just started in Midwest winters but never really had issues when hot. Since I’ve only had 4EATs in my most recent OB & Impreza, the Gear 300 I’ve bought over the years has lasted longer, so I had a quart I would sacrifice for a few members’ info prior to buying.
I did miss that you don’t have any stick Subies until way after I wrote that reply.

Partially due to your thread here I may be trying the HPL 75W90 in both the STi 6 speed and LSD’d 5 speed and will report when it happens…
 
I did miss that you don’t have any stick Subies until way after I wrote that reply.

Partially due to your thread here I may be trying the HPL 75W90 in both the STi 6 speed and LSD’d 5 speed and will report when it happens…
I’m sure @High Performance Lubricants will be interested in your feedback. Make sure to PM him once it’s on your trans and you’ve got some miles on it. 👍🏻
 
Constrained how? What are you asking?
Yes, appears “sold out,“ “discontinued,” ”backordered,” “out of stock,” or whatever, at every online source I tried a couple days ago. Too bad.

nothing against HPL or Amsoil, because i have no experience with either in the Subaru, but I personally felt comfortable that mixing the LW Shockproof with the Motul worked great. Much less “notchy“ “crunchy” than whatever the dealer put in when they talked me into one of those standard mileage based “services,” (probably around 75k), and I think also better than whatever it had in it when I bought it used @ 51k miles (probably factory fill)…but that’s pretty far back in my memory banks. Ambient temp here is 20f to 108f, and obviously MT’s get a little balky at low temps (and things can be much worse than 20f in other parts of the country). One opinion I remember was that Motul helped in lower temps, whereas the LWShockproof is what provided the “crunch-free” experience.

I know the Redline tech I spoke with back then didn’t like this mix, nor mixing Shockproof with his own 75w90LS, but back then, the Internet guru’s at LegacyGT.com didn’t like the Redline 75w90NS straight up either. It’s interesting that today, Redline specifically touts Subaru MT’s as a great candidate for their LS (along with Porsche).

again, I’m not sure how relevant this is to anyone who doesn’t have an older Subaru “Hi-Perf“ 5-speed
 
@Impatient i used all of these fluids as well. The RL 75w90NS was probably the best feeling in cold weather straight up; the G300/Shockproof was probably the best overall, but VERY pricy all things considered. Looking at the cold flow Brookfield & viscosities I think we start to see why G300 is hard to shift in cold weather; it’s got a thinner KV100 but a 33% worse Brookfield viscosity which is -40*C.

I haven’t seen Brookfield #s for anything other than these 2 (but again, I haven’t been looking since I sold my last stick) but based on these it seems to correspond to personal and internet experiences for manual transmissions- lower Brookfield results seem to indicate cold-weather engagement ease and KV100 would indicate hot-weather engagement smoothness. @High Performance Lubricants is this take fairly reasonable for a simple understanding?
 
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@Impatient i used all of these fluids as well. The RL 75w90NS was probably the best feeling in cold weather straight up; the G300/Shockproof was probably the best overall, but VERY pricy all things considered. Looking at the cold flow Brookfield & viscosities I think we start to see why G300 is hard to shift in cold weather; it’s got a thinner KV100 but a 33% worse Brookfield viscosity which is -40*C.

I haven’t seen Brookfield #s for anything other than these 2 (but again, I haven’t been looking since I sold my last stick) but based on these it seems to correspond to personal and internet experiences for manual transmissions- lower Brookfield results seem to indicate cold-weather engagement ease and KV100 would indicate hot-weather engagement smoothness. @High Performance Lubricants is this take fairly reasonable for a simple understanding?
This prompts me to ask the (noob) question: what temperatures does a typical rear diff…or typical Subaru transaxle…experience? I was wondering if 100C is only experienced in extreme situations? I could be persuaded that 100C is not the normal operating environment, unless towing…or racing. But what do I know.
 
Well, some (or many) people might want to see that tested, but there is also a RedLine 75w90 without friction modifiers…confusingly labeled 75w90NS.
Just to make note on this thread something that has been said before in others:
The friction modifiers that are not included in 75w90NS are ones added to GL-5 blends so as to modify the friction for LS Diffs. However, the friction modification chemistries used on those materials are different from those utilized on synchronizers. Leaving out one (mostly unrelated) additive may alter the CoF in a minor way, it won't be as effective as adding and tailoring the blend on the frontside with specialized additives. This is the main reason I don't include it as a prime option for Subie/Porche owners--and in my first comment. If Redline were to come forward to one of our staff members or the site as a whole and show evidence that it is primarily engineered as a GL-5 MTL, we could all benefit. (Especially due to availability issues of late.)
 
This prompts me to ask the (noob) question: what temperatures does a typical rear diff…or typical Subaru transaxle…experience? I was wondering if 100C is only experienced in extreme situations? I could be persuaded that 100C is not the normal operating environment, unless towing…or racing. But what do I know.
I agree, it’s a good question. I would honestly think that 100C is unlikely in an NA Subie in just about any situation… STIs are likely on track days I would imagine. On the NAs, you’re talking about ~55HP max per differential, so there’s likely not a ton of heat generated there. But yes it’s just a WAG right now.
 
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I agree, it’s a good question. I would honestly think that 100C is unlikely in an NA Subie in just about any situation… STIs are likely on track days I would imagine. On the NAs, you’re talking about ~55HP max per differential, so there’s likely not a ton of heat generated there. But yes it’s just a WAG right now.
yeah, I don’t track my Subaru, but it is the more powerful turbo version, FWIW. That said, I don’t stress the “high” temp even in aggressive street use in Texas heat, but there could be a balancing act between “crunch-free” cold shifting and overall durability with the thinner Motul.

But, I am following this thread also on behalf of my Ford Transit van (typical Ford 9.75 open rear diff…which might get upgraded with an Eaton TruTrac soon; it has the super low 3.31 ratio…or is that super high?), and so the temp question I’m asking is for its benefit as well: what is typical differential temp range of a full-size American pickup or SUV, towing or not towing? I figure the 9.5ft tall Transit falls somewhere between an F150 towing and not towing, because of the high-roofed van’s aerodynamic drag, …or for that matter when crawling up steep forest roads In the mountains. I know there are a lot of “thickie’s” in the Ford world, using 75w140’s instead of the factory 75w85, which has me concerned as well, perhaps being “too thin.” Even Amsoil appears to “suggest” customers use their 75w110 for “more protection“ than their 75w90 can provide…I guess I am drawn in by the “thickie” argument again.
 
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Just to make note on this thread something that has been said before in others:
The friction modifiers that are not included in 75w90NS are ones added to GL-5 blends so as to modify the friction for LS Diffs. However, the friction modification chemistries used on those materials are different from those utilized on synchronizers. Leaving out one (mostly unrelated) additive may alter the CoF in a minor way, it won't be as effective as adding and tailoring the blend on the frontside with specialized additives. This is the main reason I don't include it as a prime option for Subie/Porche owners--and in my first comment. If Redline were to come forward to one of our staff members or the site as a whole and show evidence that it is primarily engineered as a GL-5 MTL, we could all benefit. (Especially due to availability issues of late.)

hmmm. Of my 2 vehicles, I was thinking the Subaru is the more finicky, given it’s got a transaxle, but because I’m thinking of modifying the rear diff of my Ford to include a TruTrac Torsen unit, which Eaton says doesn’t like FM’s, I’m concerned about any fluid with FM’s for either vehicle.
 
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